This little wasp seemed to be observing itself while flying in front of the mirror in the bathroom. It is a male Tromatobia lineatoria [1,2] (confirmation Fons Verheyde).
With Fitton’s key  the following characters are decisive:
- face and orbits yellow yellow + face male completely yellow (photo 1,2,4,5)
- rear edge pronotum + ‘subalar prominence’ yellow (photo 2)
- abdominal segments black and apical edge often reddish (photo 1,2)
- yellow orbit makes sharp angle behind the rear ocella (photo 1)
- hind trochanter and trochantellus at least partly cream white and with light spot on femur apex (photo 1,3)
The characters in this key lead to the species T. occulatoria, which is an misidentified older name for T. lineatoria .
Because it was already the end of the year and the species does not overwinter I did not release it and eventually added it to my collection, see here.
References1 Nederlands Soortenregister
2 FITTON, Michael Geoffrey, et al. Pimpline ichneumon-flies. Hymenoptera, Ichneumonidae (Pimplinae). Pimpline ichneumon-flies. Hymenoptera, Ichneumonidae (Pimplinae)., 1988, 7.1.
3 SHAW, Mark R. Notes on British Pimplinae and Poemeniinae (Hymenoptera: Ichneumonidae), with additions to the British list. British Journal of Entomology and Natural History, 2006, 19.4: 217.