The Ichneumonidae is the largest family of insects in Britain, with well over 2,000 species ranging in size from individuals 3" long with 3" ovipositors (which is big for a British insect!) to tiny ones only 1/10" in length. The family is divided into a large number of subfamilies and the larger ones are further divided into tribes. There has been a consistent trend to elevate tribes to the status of subfamilies, and this continues.
Dr Gavin Broad, the ichneumon specialist at the Natural History Museum in London, has prepared a key which will allow an ichneumon to be placed in its appropriate subfamily: https://www.brc.ac.uk/sites/www.brc.ac.uk/files/pictures/resources/ichneumonidae-subfamily-key.pdf
In this introduction are listed some of the published identification keys that can be used to identify British ichneumons. In addition, there are a number of unpublished translations of key works published in French, German and Russian. The publication of a key naturally generates more interest and work on that group, with the result that additional species are added to the British list (or described as new to science). The listed works may not, therefore, always be entirely up to date. As a result, it is more than usually important to build a collection so that specimens can be compared with correctly-named vouchers and any insect which does not match the decriptions well should be retained, as it may be something new.
Dr Broad has also prepared a checklist of British ichneumons: https://bdj.pensoft.net/article/9042/download/pdf/
In the past the subfamilies were arranged in what was believed to be the most natural arrangement but there are several ideas about what this should be and this checklist avoids the question by arranging the subfamilies, then the tribes, then the genera and finally the species in alphabetical order.
Ichneumons have been included in several locality lists, such as:
Coldwell, J.D. (1999) “Insects of the Barnsley Area.” Sorby Record Special Series 12
Skidmore, P., Limbert, M. & Eversham, B.C. (1987) “The Insects of Thorne Moors First Supplement.”
Walsh, G.B. & Rimington, E. (1956) “Natural History of the Scarborough District.”