Trevor’s Travel Trivia – Part VIII – Thames Trivia


Frost Fairs

Perhaps my favourite Thames trivia is this first one here. In the olden days the Thames was much wider and hence slower-flowing. This meant that it regularly froze over in winter. Londoners used to do so-called Frost Fairs on the Thames, even though that hasn’t happened since 1814.


Pics free stock photography except where otherwise noted. 2nd pic (c) BerkeleySqB

Either the longest or the second longest river in the UK

The Thames is usually considered to be the second longest river in the UK at 346km. It’s said to be only exceeded by the Severn, which is supposed to be 8km longer at 354km. However, one of the lesser known Thames trivia is that the river Churn, a tributary which flows into the official Thames about 15km downriver from its current official source, is 37km long. If you’d consider the source of the Churn to be the source of the Thames, then you would add 22km to the ‘new’ Thames. This would make the Thames 14km longer than the Severn.

It’s not just the country fairs to avoid in the English countryside

I’m sure I’ll get some flak for including this one, but I think it belongs in any list of Thames trivia: Don’t just avoid the country fairs if you’re in the English countryside and want to live. On average one dead body gets pulled from the Thames every week.


These 2 pics (c) BerkeleySqB

Locks & bridges

The river has 45 locks and is spanned by more than 200 bridges. The longest is the Queen Elizabeth II Bridge which is 812 metres long. It is also crossed by 27 tunnels, six public ferries, one cable-car link, and one ford.

Islamic State of Iraq and Syria?

Around Oxford the Thames is called Isis. Of course the Learned Ones could not simply call it the Thames like us common folk. Not out of character, they got this one wrong too, in more than one way.

The local establishment thought that its ancient name Tamesis was somehow a combination of Tame Isis. They knew that there are a number of UK rivers that are called Tame or similar, so they abbreviated the name to Isis. In actual fact the origin of Tamesis is the same as that of the other rivers that are called Tame and is thought to mean “dark”, “dark water”, or “water” in various languages such as Welsh, Brittonic, and Middle English. Tamesis was just the Latinised version of one of those original terms such as Tamesas, Tamēssa, or Tafwys.

Unsurprisingly, a lot of local businesses with references in their names to the river Isis quickly changed their name when the situation in the Middle East changed two decades ago. Isis Solutions became Tamesis Wealth Solutions, and so on.

1st pic (c) The Indpendent, 3rd pic (c) New Scientist

Wild Wildlife – Check out these Thames Trivia

There are otters, seals, and lampreys in the river, even in London. Lampreys are fascinating creatures that have remained unchanged for hundreds of millions of years and survived at least four global extinctions. Instead of a mouth they have a so-called oral disk with 150 or so razor-sharp teeth. Hollywood has done a fabulous B-movie about them called “Blood Lake: Attack of the Killer Lampreys.”

Far-travelled residents

The Canada geese along the river have never seen Canada. They stay in England all year round ever since they were introduced. However, every single eel in the Thames started its life in the Sargossa Sea, off the U.S. coast. The tiny creatures then swim 5,000km and more to the Thames and other European river estuaries. They swim up these rivers and live there happily for 20 years before returning to their birth place to give birth to their own kiddos.

High eels

It’s sad that two years ago researchers from highly reputable King’s College found that the reason for wide-spread hyperactivity among eels in and downriver from London is due to the large amounts of cocaine in the river water. Londoners snort their lines like there’s no tomorrow, not just on the weekend. The cocaine leaves their body with the urine and ends up in the Thames where it gets absorbed by highly sensitive eels.


Right pic (c) Zoological Society of London.

Pregnant males

Some inhabitants of the Thames river are pregnant males. The short-snouted seahorse, which inhabits various stretches along the Thames, including London, is the only known animal species where the males get pregnant and give birth to their young.

Talking gender fluidity

There are plenty of oysters in the Thames estuary. Up to Southend-on-Sea the estuary officially forms part of the river Thames. These molluscs switch between male and female during their lives. As far as Thames trivia go, this one must be among the weirder ones. One breeding season oysters are male, the next season they are female.


Right pic (c) BerkeleySqB

Thames Pearls

Oysters produce pearls, and so do the Thames oysters. Unfortunately they are dull and of no value.

Whale of a time? Far from it.

Sadly, a sperm whale and a fin whale died in the Thames a year ago just days apart. They are the 2nd and 3rd biggest mammals on earth, only outdone by the blue whale. Many smaller whales like humpback whales have been spotted in the river over the years. Some as far as Battersea. Dolphins have even been spotted in Richmond. Many of these marine mammals make their way back into the open sea. The river is not their natural habitat and they cannot survive there for long.


1st pic (c) Chiswick RNLI, 2nd pic (c) Universal Pictures, 3rd pic (c) Sportex Italia

All’s well? Well, if you like Wels.

Wels catfish were introduced into the river in the 1930s. They thrive to this day. In 2008 an angler near Kingston pulled out a huge specimen. He wasn’t able to weigh it, as his scales only went up to 22.5kg and the fish was way more than that. So he released it back into the water.

In 2013 police were called to an alleged body next to the Thames in Richmond, only to find the carcass of a giant catfish. In 2019 there were multiple reports of experienced fishermen of a 1.8m long wels spotted near Tower Bridge. Catfish are known to grow to over 2.75m in length and over 140kg in weight. There have been credible but uncertified reports of specimen 5m in length and over 300kg in weight.

Talk to any fisherman around Walton-on-Thames and they’ll tell you about the Walton Bridge Monster with the same thousand yard stare you know from Robert Shaw in Jaws. Perhaps most shockingly, wels even sometimes intentionally beach to get some land-based protein, like orcas do with seals.


At least five species of shark are regularly spotted in the lower parts of the Thames, such as dogfish, tope and starry smoothhound. They pose no risk to humans.


Oh s###!

Thanks to London’s completely overburdened Victorian sewage system the tidal Thames is one of the few large rivers in Europe that is full of s###, pardon my French. You can monitor the s### density of the Thames in real-time here. Just scroll down to the map then click on ‘Coliforms’. Luckily most animals don’t mind human faeces too much. In terms of chemical toxins and other pollutants the river water quality has made huge progress during the past few decades and is not looking too bad.

World Poohstick Championships

Talking poo, the World Poohstick Championships are taking place each year on the Thames near Day’s Lock.

Thames Tummy and swimming heroes

The first person to swim the full length of the Thames was Lewis Pugh in 2006, way before the very very cool David Walliams did his charity swim. Both of them got violently ill. There’s a name for it: Thames Tummy.

Deadly disasters

The deadliest disaster on the Thames occurred in 1787 near today’s London City airport, when the Princess Alice sank and 700 people perished. 202 years later, in 1989, 51 people died when the Marchioness sank in under 30 seconds near Southwark Bridge.

Bunkers – bonkers?

Even on the upper parts of the Thames, you can still see dozens of WWII bunkers, which had been erected to fight a possible German invasion along the Thames. From today’s perspective the risk at the time of German destroyers wiping out Lechlade or Buscot seems minimal, but that’s with the benefit of hindsight.

Don’t let these Thames trivia put you off one of the best things in London life: enjoy the river

As mentioned at the beginning of this post: Please do not let any of the above mentioned facts put you off enjoying the beautiful Thames. I go swimming and stand-up paddling in and on the Thames, incl. in West London. While I try hard to avoid swallowing water, I never feel unsafe. I follow all rules and use common sense.

I watch out for tipsy motor yacht captains, not for catfish or lampreys. Wels are not very scary, even big ones. They are obese wobbly lazybones that mainly feed on worms. The ones that beach, are tiny and do so to catch pigeons (video here). 4 out of 5 times they don’t even catch a pigeon. No fisherman in Walton fears the so-called Walton Bridge Monster. They just want to catch it for a good picture and then release it again. Most likely it will be around 30kg, which is about as big as they get in the Thames, and they’re certainly no risk to humans. Sea lampreys and all the other lovely wildlife are nothing to be afraid of either.

You’ve probably swum with Great Whites

No lamprey has ever attacked anyone in the Thames. They are parasites, not maneaters. The Queen eats them and loves their taste.

You’ve probably had a swim in waters where great whites live, like anywhere in the Mediterranean or most of the big oceans? And that was almost certainly reasonably safe too. Great whites are dangerous, though. Catfish or lampreys are not.

I hope you enjoyed these Thames trivia. If so, why not check out some of Trevor’s other Travel Trivia, for example the one about Papua New Guinea, about Bhutan, or about how peasants’ food turned posh?

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  1. Wow… a fascinating post, with so much history, and interesting facts about the beautiful river Thames. I do remember the awful disaster when the Marchioness boat sank, I was living in London at the time. It was so sad. I had no idea that sharks and even whales can be spotted there…wow. Also have never heard of the “Frost Fairs”… thank you for this great post.

    1. Yes.. that Marchioness disaster sounds like it should’ve been impossible to happen in the capital of a wealthy country in today’s time… So glad you enjoyed this post. I’m starting to tuck into your Cornwall series at the moment, great stuff! 🙂

  2. The Frost Fairs sound like fun. In Ottawa the river freezes and there is a winter festival on the ice for many weeks. At least with the Thames frozen it might be harder for the bodies to be discovered! I never knew there were so many locks on the Thames. The engineer in me would love to explore those. But what a strange collection of things living in the river. Certainly not swimmable for me!

    1. Oh.. you Canadians live in bliss with regards to any kind of winter fun, I know!!! 🙂

      The locks were a real problem for my buddy and me when we started our first leg of our Thames source to London stand-up paddle earlier this month. It just takes soooooo much time to portage around them. In the end we started to become more successful at talking lock keepers to let us go through their locks (rather than portaging around them), which saved a lot of time, even though it’s not strictly speaking within the rules of the authorities… 🙂 🙂 🙂

      If you say it’s not swimmable for you, then I’m worried I did put you off with all those fun facts about wildlife. That’s exactly what I didn’t want to happen, oh no… Perhaps I’ll change the post and avoid mentioning catfish and lampreys….. I’ll see…

  3. What a fascinating post. I was particularly interested in the quantity and variety of wildlife that can be found in and around the river. And I had no idea that the Thames hosted the World Poohsticks Championship – this is completely brilliant!

    1. Cheers, Mitch. Glad you enjoyed the read. The World Poohsticks Championship is quite a fascinating topic, yes. You can find Youtube videos that have the same vibe as reporting from a major sports event, including interviews with main contestants (the poohstick throwers, not the poohsticks), where they explain their technique and which comparative advantage they hope to gain from it. Quite hilarious. 🙂 🙂 🙂

  4. We took a river cruise on the Thames and don’t recall any of these fascinating bits of trivia. Thanks for the local insider’s fun and weird facts!

    1. Thank you, KMF, appreciate the compliment. In all honesty, I think the tourism and hospitality industries don’t want to tell people about all the creatures in the river as it might not be that great for business, in particular not for water-based activities like paddling or swimming.

  5. What a fascinating post I never realised there where seals in the Thames. 200 bridges is a huge but I suppose at 346 km its not unexpected.
    Lewis Pugh is mad swimming all that id say Thames Tummy would of been the least of his worries

    1. Thanks for reading, Richard. Yes, Lewis Pugh is probably a bit mad, then again, he’s more or less a professional long-distance swimmer. I’m even more blown away by David Walliam’s, the comedian’s, performance. 🙂

  6. Omg so many fun and slightly gross facts about the Thames! I’ll never look at the Thames River the same. Haha. Not sure if I’d want to swim in the water but I’d like to try SUP there one day. Can’t get over the size of that catfish!

    1. Thanks for reading, Vanessa. Glad you enjoyed the post. I really hope I didn’t put anyone off swimming in the Thames. It’s safe if you swim west of central London and avoid swallowing water. 🙂

      Stand up paddling on the river is a great deal of sheer fun.

  7. Oh crap, this was a fun read. I will never see the Thames the same way again. I’ll sure never get in the water because so many creepy creatures in there. I didn’t know that London prepared for an invasion by the Thames either.

  8. Looks like I could afford myself to get some correct answers on The Chase or The Mastermind all thanks to the Thames trivia 😉 What amazes me are the oysters that inhabit the estuary that tell us something about miracles in nature, the science or social agenda.

    1. Yes.. those gender-fluid molluscs are quite something haha… I wonder if a widely witnessed wave of wokeism in the water was inspiring oyster outings.

  9. We’ve got friends who live near Oxford, on a boat, and are very proud of their Thames connection. I must remember to ask them if they’ve ever seen a metres-long catfish.

    1. I’d imagine most boat owners on the river probably won’t have seen any catfish, big or small. I doubt that catfish would go through locks and they certainly couldn’t jump up weirs like lampreys or salmon. My guess is they’ll only be found in the tidal Thames, but it’s an interesting question. Please keep me posted.

  10. Ha-ha brilliant post! I love walking along the Thames but no way would I ever consider getting into it as I also had heard about the high levels of s**t in it. Had no idea about the levels of cocaine, though, but after working in the city for over 15 years, it makes sense! I remember the Marchioness sinking, tragic.

    1. I knew you lived in Old Blighty, Wendy, but not that you worked in the Square Mile for such a long time, wow..!! I’m just pleased it wasn’t my post that put you off swimming in the Thames.

  11. Do I even want to know what poohstick is? You definitely don’t encourage me to go swimming there, but then again I always seem to swallow water. Thames tummy for me. Great work on this post, it’s really entertaining and some great facts. Now to find lamprey movie.

    1. Thank you, John. Appreciated. Poohstick contests are inspired by Winnie the Pooh and involve people throwing sticks from a bridge on the upriver side. Whichever stick arrives on the downriver side from under the bridge first wins. Oh.. and you won’t regret watching Blood Lake.. one of the best movies ever.. right up there with Metropolis, Citizen Kane, Sharknado 4, Nude Nuns with Big Guns, and Lesbian Vampire Killers… 🙂 🙂

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