Doesn't the south of England have a foot or so of water heading down river to London atm? 'Cause you know the Top Gear crew's prepared, all they have to do is un-mothball their amphicars and borrow some more gear from Gibbs. Not to mention the stuff they've picked up raiding the UK MoD auctions. (Knowing Hammond if he could front the cash, all the ex-mil Land Rover's would be his. So in this situation an amphib land rover would be on his shopping list.)