Andy,
welcome to the forum. I was very interested to read your post, for obvious reasons. I would very much like to see your photos of the tanks, I am always hopeful of finding one of mine.
Capt. Clapperton was troop leader of 2 troop, his wireless station was 6.
Your dads tank, APACHE, T189521, was an original 1st RTR tank and was a 75mm Cromwell IV. It's commander was Sgt G McKee. ACHILLES, T189511 was also an original IV and was knocked out on 14th June. ALEXANDER and ASSASSIN were replacement tanks.
I hope to soon see some pictures from Capt. Clapperton, your dad may be amongst them.
If you could get some copies of your dads photos of the tanks, I would be very grateful and of course cover any costs. Posting them here would be great too!
Adrian