Neil Jones wrote:
Sue wrote:
"John Burke" wrote
Sue wrote:

A Comma perhaps?
http://en.wikipedia.org/wiki/Comma_(butterfly)

Similar, but the profile of the wing was an arc, not in angular
sections as the Comma's. Also the speckles were uniform (and all of
a same dark colour).

The combination of the vivid primary orange and the secondary
(almost black) dark markings made me wonder if signalled something
nasty for a predator.

Sounds like one of the fritillaries. Picture/info links here might
help identify it:
http://www.butterfly-conservation.or...ata/index.html

With dark specking on an orange background I'd say that is possible.

I looked through Sue's link but all the fritillaries there have a complex
geometry in their wing shapes and colour patterns, where this one didn't.
Also the orange I saw was far brighter than the amber that the fritillaries
seem to have.

A Wall Brown is another possiblily but the colours are not that vivid.

The only fritillaries that are likely in Hertfordshire are Dark Green
or Silver Washed. The others used to be there but they have
disappeared.

I didn't see this in Herts btw, but in the back garden of a friend I was
visiting in inner London.

How big was it?

Average? 40 - 50 mm wingspan? Its size didn't seem to be an
outstanding feature.

Like butterflies everywhere in the UK there has been a massive
decline.

Yes. I know little about them but they certainly seem less common than I
remember.

Neil Jones
http://www.butterflyguy.com/

I'll do a search at your website later and post back if I can find it.

Thanks.