Got home dry but exhausted .Overtook a cyclist on the way and was feeling chuffed until he told me he was recovering from open heart surgery which rather spoilt the feeling of achievement) Washed up etc 1hr plus (with Chris's valuable help) Cut the lawns ,did some gardening then collapsed onto the bed ....
Further to our breaktime discussion on the origin of sayings ...Hoist by his own petard..
The phrase's meaning is literally that the bomb-maker (a "petard" is a small explosive device) is blown up ("hoisted" off the ground) by his own bomb, and indicates an ironic reversal, or poetic justice.
I knew you were dying to have the puzzle solved.