My memory of the insect, was that it was about 20mm long, which is a bit big for that and it appears to have a white patch on its back and the top of its back legs. Still memory is a funny thing and taking the parsnip flowers at about 1.5mm, it could be a large individual. The link you gave me has the wasp on the same flowers!
Thanks for your idea. David.
I think it's an ichneumon, maybe a Virgichneumon species.