Crusader AA: Rob, you stated in the Journal that these were fitted with "20mm Oerlikons". Actually they came in two flavours:
- Crusader AA mk1: single 40mm Bofors
- Crusader AA mk2: twin 20mm Oerlikon or Polsten
Yes, they did see significant ground use during the short period of the fighting in Normandy. The Poles in particular are noted for using theirs (AA mk2) against ground targets throughout Normandy and the rapid pursuit into the Low Countries. They lost them during the refit over winter 44-45 in the Netherlands.
Crusader AA mk1:
Crusader AA mk2:
Bascially they stuck the turret from a Crusader AA Mk2 onto the Centaur hull, although being a late mod these seem to have exclusively got the version with the Polsten guns instead of Oerlikons. I don't know how much action these saw, the Centaur was tragically underpowered and I can't imagine them being in the forefront of the Allied advance very often.