Is this a Giant Ichneumon?
Great site. I had this bug on my windscreen for two hundred miles un a journy between my house and my parents. Have asked friends but none of them has ever seen one before. looking at your site I presume it is a Giant Ichneumon? Do you know if they are very common in England?
We spent some time searching for information and cannot determine if Giant Ichneumons in the genus Megarhyssa are native to England, but we did find some information about them being imported to use as biological controls for wood boring larvae. This is a Megarhyssa, but we are not sure of the species.