I have three Duchamp shirts and ties ....
purchased last Boxing day on sale. They will have a sale at end of season wher you can save from 40% to 50%. All of their stuff is quality, but I had a problem with their St James double-cuff shirts (120, 2 fold). Their shirts run small in neck size, but the sleeves run long and they only have one size of sleeve length per neck size. I ordered my normal size (16" neck), but it was two small. I have bought a lot of Jermyn street shirts, and this was the first time a 16 did not fit. I had to return the shirt which cost me $17.
The replacement shirt and the two others fit very well (16-1/2 neck) but the sleeves were much too long. They put a gusset button on their shirts, so I almost ran out of room in shortening the sleeves. The shirts now fit well thanks to mt alterations person, but the gusset button is now a little less than one inch from the double cuff.
I got three shirts and three ties for 50% off, but their shipping charges are high, about $36. Also I had to pay duty since they ship UPS who charges duty plus a fee. So the 50% off savings was rapidly eaten up by excessive shipping charges, duty plus courier fee, and alterations charges by my tailor.
When they have another sale, I'd like to get some ties (38 bps on sale), but I doubt if I would buy any more shirts. Too much of a hassle, and the fit is not the best because of the gusset button problem. I would reccomend that you don't buy their shirts unless you are situated in the UK and can try them on before buying.