WW2 British Army insiginia

The male lead in the recent romance/tragedy Atonement served in the British Army and was at Dunkirk. Anyone recognize the cap insignia? Did it/does it really exist?

http://www.lailalalami.com/blog-old/archives/atonement_film.jpg

And what’s the thing on his left sleeve here?

I thought it might be the Royal Sussex, but it doesn’t look quite right.
The brown paper thing is a gas detector paper worn as a brassard. These things were supposed to change colour in the presence of gas. You see them to an extent in 1939-40 as both sides were braced for chemical warfare at this point. Later on most anti-gas equipment was discarded, although it was all issued again for the invasion in '44.

It’s supposed to be the Royal Sussex. Cite. Their badges actually looked like this, though.

Just took another, closer look at the Atonement DVD, and you’re right. There’s a closeup of Robbie Turner at the 0:56 mark, just after Cecilia shows him the postcard of the seaside cottage, and on his cap you can clearly the two-toned badge shown in the left-side image of the link below. Two minutes later, at 0:58, when Cecilia drops her letter in the postbox, you can see it’s addressed to Robbie in A Company, 1st Battalion, Royal Sussex Regiment, BEF.

Thanks again.

http://www.northeastmedals.co.uk/british_regiment/royal_sussex_regiment.htm