Help identifying bike

[Andrew V]

Hi all.  First post.
This is a picture of my father in the early 60s. 
I'm keen to properly identify the bike.
I think it's a c10 or c10L but I'm not totally sure. Hoping others with more knowledge would help identify.

Kind regards
Andrew

[JulianS]

Looks like a C11G - you can see the rocker box, so overhead valve, and the primary chaincase bulge to take an alternator.

[Andrew V]

Thanks very much.