64 year old cyclist Richard Smith got quite the surprise when out on his bike near Reading. Let's have him describe it in his own words: "I was cycling on my own and I saw what I thought was a bough of a tree with four stubby branches on it close to the bank.
"As I got closer I saw it was a crocodile. It was about 4ft long. It had a 2ft tail and a 2ft body. I got off my bike and ran back to where it was, but it had gone. I ran along the river for about 50 yards but it wasn't there anymore."
As well as Smith, a local tackle shop worker also claims to have seen the beast pull a fully grown swan into the water and has warned that it's only a matter of time before the odd dog or two become the latest victims.
However, reptile expert Shaun Foggett has poured cold water on the claim and said that crocodiles would struggle to survive in an English winter.
The Thames has previously housed dolphins, porpoises, seals and even a 7-tonne bottlenose whale.