1955+/-, multiple identical circular saucers in formation, spinning, slow-moving, low, 30' dia.?, visual only.

Rural area, near RAF Great Rissington, Gloucestershire, U.K.
I was an avid plane-spotter, was watching-out for planes, with binocs. This was an area frequented by test-planes and many U.S.A.F. bombers (I think I saw the U2 at extreme altitude before it got any publicity.) That day, one circular saucer rose above hilly wooded horizon, about 2 miles away, edge on, travelling not very fast in hztl. plane, banked away, clearly spinning (about 50-60 r.p.m., I'd guess), rose a little above the horizon, then fell away below horizon, TO BE FOLLOWED BY 8 MORE IN LINE ASTERN. I had the binoculars on it (them) in turn and I can't remember if there were two visible at any one time, but the timing and motion was such that it wd be highly unlikely if it were one repeating the manoeuvre another 8 times. Colour was aluminium grey.  Dia. about 25-40', I'd guess -- at that distance it was difficult to tell. I didn't get a long look edge-on but I think I glimpsed a bulge at the centre.
Have spoken about this for years and, of course, everyone dismisses it. Got my Dad to report it to R.A.F., but .... you know the rest!
Witness indicates that the date of the incident is approximate.  PD