'Junk' or S/H shops in London

[Answerprancer]

Does anyone know if there are still streets or areas in London that have a high concentration of Junk/second hand/antique shops.
I mean real 'rummage around' potential bargain opportunities, not pretentious poncified over-priced fashion shops.
I'm after photography stuff.
Thanks
AP

[boxtops]

Portobello Road market? - London's a huge place, there must be one somewhere.

[Answerprancer]

Thanks - I wonder if it runs on Saturdays.