Correct way to button a three button jacket ?

Can anybody please tell me if there is a rule on the correct way to button a three button jacket. I have just bought my husband a new sportscoat and he thinks the middle only done up looks good but I prefer the top and middle done up otherwise his chest looks too big. Most of the magazines show top and middle done up but looking at period drama shows and photos it seems they only buttoned the top one. So I was wondering if anybody can shed any light on this. Thanks

Carol