Does this stem from Jenbel's comment in the BA forum that she and the entire British embassy staff searched on a Sunday in Tokyo for a jacket for a 6ft 4in tall guy whose luggage was lost by BA... but to no avail... and the entire group decided to go to their meeting the following day without jackets so as not to embarrass him?

I don't know what the British embassy staff tried... If the clothes at Isetan didn't fit, perhaps they could have checked their network of friends to find a very large foreign resident of Tokyo to lend them a jacket for a day. Perhaps they were busy averting a trade war or attending a cocktail party.

The "on a Sunday" is a red herring; Sunday is a fine day to go shopping in Tokyo. However, it is certainly true that Japanese clothes aren't designed for European/American proportions. You can find Gap, Zara and so on - but they won't necessarily have all the sizes that you would normally find in the Edinburgh Gap or Zara. If you're medium sized (as Q-Shoe described) then you will find stuff that you can wear - although when you find a shirt in your collar size, you may find the sleeves too long etc.. But if you're tall and big, then your options are very limited.

If you're in the enviable position of being able to claim against insurance, I suggest you try Isetan's "Super Men's" department in Shinjuku. Price performance is bad, but they stock a lot of big and tall sizes:
http://www.isetan.co.jp/icm2/jsp/sho...mens/index.jsp

I think there's also a store with large sizes near Shinbashi - I'll try to find the name and address.

The Isetan store claims to cater for men up to 195cm tall. But frankly speaking, if you're that height with a European build, you may find that nothing off the shelf hangs terribly well.

But really, if BA's bad reputation for losing luggage concerns you - and you need to have some business clothes in Tokyo, then you're probably best off wearing a jacket, a good pair of slacks and a smart pair of shoes for the flight. (and a spare shirt in your carryon).

BTW - While writing this response, I was thinking of the need to buy decent looking business attire. If you're just looking for jeans and sweatshirts, then I'd try Uniqlo first.