I think one of the problems is that many of the outside stands are not selling antiques but modern reproductions, mobile phone cases and London souvenirs.
These stands are seen first and create the wrong impression. They crowd the entrances of the arcades that are selling antiques and make the entry into these arcades difficult, thus putting prospective customers off. The arcade owners have allowed to this to happen.
Having read the reply regarding various mystery objects, I too have a mystery object.
This item has been on the Fleaglass website but has received no response as to what it is. The length of the case is 5in (13cm) and the item is made of steel.
Ex-Portobello Road dealer