Is it true that it would be impossible or near impossible for the Thames river to freeze? I heard a while back that it's something to do with the Thames barrier creating too much movement in the water to allow it to freeze.
Later than the ice age Tigger - the last frost fair (held on the river when it froze) was 1814. There are other reasons besides the thames barrier which would make it hard to freeze now - it's not the same river it was back then.
I'd also think that what you heard was the wrong way round.
The Themes is highly unlikely to freeze because it's tidal further up river than London meaning you have the tidal movement and the salt helping to stop it freezing, I would think the Themes barrier is going to make more likely to freeze if it's shut.