The biggest adder I've seen was on the coast path near Salcombe. t least when basking in the open you have a chance, because they instinctively coil to strike. That one was a couple of feet I suppose, but I wasn't looking down so could have stepped on it, were it not for the "SNAKE!" shout!
We've seen a few others but all like pencils, and are quite cute as they coil their six inches to strike.
