I happened to be on a work related expedition to Hook near Basingstoke last Tuesday and since it was such a nice day I decided to go exploring once I was done. So I drove a little bit south to visit Odiham Castle!
As ruined castles go, this one is pretty good, with informative information boards aplenty. Apparently it was the place when the king set off to sign the Magna Carta and later was besieged by the French!
The nearby canal is quite pleasant although blocked by an impassable tunnel.