[Salmo]

I found this on my compost heap. I was strikingly beautiful so I thought I would share it with you.

Does anyone know what it is?

[Trillium]

I'd say it looks more like a wasp, perhaps a beowolf wasp

http://www.pbase.com/crocodile/wasps

[Rangerkris]

Its what they call a wasp beetle, well it looks like one to me. I am no expert tho.

Taken from Natural England site

The wasp beetle is a brilliant mimic. It is very dark brown with four conspicuous stripes across the wing cases. Not only does it look like a wasp, it even acts like one, moving jerkily with rapid stops and starts as a wasp will do. This mimicry is for its own protection as potential predators will leave this completely harmless species alone.

It is most often seen on umbel flowers such as hogweed or angelica in June, but can also be found on tree bark or on fences. Its larvae live in hard, slightly decayed dead timber, usually of willows and birch. Common throughout most of England, the wasp beetle is more local in the north.

Food
Wood-feeder as larvae, on hard, dead wood in the early stages of decay or in exposed dry situations where fungal decay is slow. Adults feed on nectar and pollen of flowers.

Plants
Crack willow, Downy birch, Goat willow, Hogweed, Pignut, Silver birch, Wild angelica

[Comfortably Numb]

I agree with Rangerkris, it's a Wasp Beetle 

Some pics here
 
http://www.arkive.org/wasp-beetle/clytus-arietis/

[Salmo]

Thank you to you knowedgable ones. The natural world never ceases to amaze me.

[viettaclark]

So it's one of the good guys!
I found a HUGE hornet-like thing down the garden but didn't kill it. Looked it up and it's a woodwasp which looks really dangerous with a long sting but it's actually it's oviposter and it's another good guy!