I've just tried it on and it is not going to button up.
It has got quite a lot of seams though so I could unpick them and let them out a bit.
The sleeve is going to be too tight as well, but I found I've put the spare fabric with it. Approx 75cm. I couldn't find this in 2016 when I found I'd not cut the insides of the pocket flaps - I sorted it with lining.
I could recut new larger sleeves, or add an underarm panel. Or change to a 2 piece sleeve
Whatever I do will need to be reflected in the lining. It needs a lining but there isn't one, so I'll have to draft it, and its not just a simple front/back setup, there's a side panel and a back/shoulder facing as well as the front facing for the lapels/collar.
I reckon that's all stuff I could tackle now, though it won't be a work jacket!