Fun, but quite easy for those of us who know stuff. Nice try with the red herrings.

The challenge here was not to find the groups, but to do so without falling for any of the red herrings. One try per group.

Good grid, relatively easy but red herrings make it fun. I would say though that Mainwaring being a fictional captain and a character in Dad's Army is a bit messy. Normally only the clue fits in two groups not the subject itself (if that makes sense).