Paul Smith men's shirts; how much difference is there between 2 collar sizes?

[Needasilverlining]

Found a beautiful vintage (OK, possibly just worn, but I'm going with vintage) Paul Smith shirt today which would make the perfect Father's Day present for DH.

Got it home and realised the collar size is 1inch greater than he normally takes. Buggerbuggerbugger. I can't obviously exchange for next size down and of course it's the only one in the shop.

Is there a massive difference between one size and another? And by any chance do Paul Smith come up really small ?

I don't know how Paul Smith sizing comes up but yes, 1 inch is a big difference in collar size. If this is a casual shirt you will probably get away with it, if it's a formal one which he would wear with a tie, the collar will be scrunched up and your DP may look like a small boy wearing his dad's shirt!

Could you shrink it a bit and then move the collar button maybe just 1cm? Might not make a huge difference but enough to make it fit slightly better. Either that or bulk your DH up to fit the shirt instead of making the shirt fit him

It's floral (gorgeous, am as would v happily steal it were it not mahoosive on me) so could be worn casually. He tends to wear quite close-fitting stuff but would be nice with slim fit jeans, just not tucked in.