Millbrook Proving Ground

What spoilt the film for me was the clear view of the High Speed Bowl track (and the tracks inside it) of Millbrook Proving Ground in Bedfordshire which wasn't even built until 1968.

I can turn a blind eye to time travel and WWI sonic weapons, but when Biggles is supposed to be dogfighting the Bosh in France in 1917 but is actually in Bedfordshire in the 80's I had to throw in the towel.