For those who want to have a look and possibly buy something - be aware - very aware. They have a lot of stock, but they also charge exxesively high prices for it. There are reported questions about returning items to them when they prove faulty. It is a long time since I visited their shop (at his older place) and to be honest some of the items he sells is, shall we say of questionable quality.
Around the corner is another company Grays of Westminster. If you are a Nikon officionado that is the holy grail. They only sell Nikon - nothing else. They are not the cheapest, but where in London is there anything cheap? But the quality of things they sell are beyond reproach.