---

Tabanidae, genus Hybomitra. Most species of this genus and Tabanus miki are the only ones with these brown dorso-lateral hairpatches (at least in northwestern Europe). Tabanus miki also has brown hairpatches on the anal segment and as they appear to be missing it must be Hybomitra. However, some Hybomitra species lack those hairpatches (montana, kaurii, lundbecki, tropica) but nevertheless the remaining species are very hard to identify in the larval stage.
By the way: VERY nice photo,you can even see the tracheal system.