Identification Required Please

Does anyone know what this strange looking fly is? Here is a shot of it's back . It landed on hubby's tee shirt and after taking a few shots we beat a hasty retreat indoors as we didn't like the look of what it was trying to poke through the material with and it was very persistent in it's pursuit of both of us. I thought it looked like some kind of horsefly but after quite a bit of research the closest I can come up with is some kind of tiger fly but the rainbow eyes are really strange and don't seem to be found on any flies that I can find - can you help? :-)

UPDATE. - I have now managed to identify this as Chrysops caecutiens (Splayed Deerfly), the females suck blood and can give a nasty painful bite and apparently it can transmit Lyme's Disease so I'm quite glad we didn't hang about :-))

I'm not going to moan about the humid heat again as I'm sure most of you are suffering too but it did bring all the insects out to play - so many to see in the garden :-))