Anna's Dad was at his flat yesterday, overlooking the river Lee, at Tottenham Hale, when he spotted a large snake swimming across the river's surface. (For views over the river see my Tottenham Hale post earlier).
This will undoubtedly be an adult Grass Snake (sometimes known as the Ringed Snake, because of its yellow collar, or Water Snake), Natrix natrix.
Grass Snakes are invariably found near freshwater - they are very strong swimmers whose diet consists mainly of amphibians such as frogs, though they will take the odd mammal or bird.
Many people think Grass Snakes are quite small - possibly remembering demonstrations on school field days etc...
This is not the case with Grass Snakes - the last one I saw in a freshwater drainage ditch on a golf course in Wexham near Slough was at least 1m long, and they can grow longer than 120cm.
Of course they are not venomous, and you will be lucky to see them at all.
Anna's father was certainly very fortunate to have seen such a beastie - (to add to the Egrets, Terrapins etc... in that part of the world!) and all a stone's throw from central London on the tube.
It just goes to show just what you can see, if you use your eyes well...
NB. The posted photo is not from me (or Anna's father), but taken from the web.
I'll just have to get back to London, and lie in wait...!