Someone wrote to me a while ago on where I usually shop for larger size jackets. This is necessary as I am not a skinny chap but one who is built like a tree trunk (I have a 48inch chest and a 41inch waist...not very tiny at all) Tailoring is the best for me AND for most larger size gentlemen out there. But it is possible to find decent ready to wear items off the rack. This was my reply.
Which jacket or blazer are you referring to? I have posted a few of my jackets in the blog. Suits I have to wear a 58IT with a drop 6 (Drop: eg, jacket size 58 a drop 6 means trousers size 52 - Italian sizes are 58IT equal to 48UK approximately) or 46 or 48uk depending on fit/cut. Drop 7 above would be a tight fit.