Can someone help me ID fly/insect

[Joyous70]

My girl is being savaged by small(ish) black flies, they look like house flies, but are a bit smaller, they swarm around all the horses and us to be fair, i have tried to look online but am unable to find anything. Im just curious to know what they are.

 

[Fransurrey]

Blandford fly? They look like house flies and pack a punch when they bite.

 

[Joyous70]

It possibly could be, my poor girl had lumps the size of £2 coins and bigger the other day.

 

[Melandmary]

Yes I think Blandford flies too. They bite my mare all over her inside legs and udder. I slather her in sudacrem in those areas to keep the flies from landing there