Christmas greetings to one and all!

I wonder if someone can help with identifying the cap badge on the attached photo, please. I wondered if it might be the Duke of Wellington Regiment (West Riding) but now I don't think so.
From my family tree I have 8 possible candidates but as I am guessing his age to be about 18-20, I may be able to reduce it to one - an Alec Thomas who would have bee 18 in 1914. The other 7 would have been 25+. They were all from Rawdon, near Leeds, Yorkshire, so I suspect it would be a Yorkshire regiment. Thank you.