St. Agnes Well
In the Well - not to be confused with the hot springs in Vancouver - are two newsagents, a film processing shop, the non-Camden branch of [Camden Lock Books]?, a clothing store, a cobbler, Nincomsoup, a gift shop, a couple of sandwich shops and Old Street Station.
Its mentioned on this web-page: http://www.kch42.dial.pipex.com/holywellslond.htm. Looks like the actual well was slightly further East, where Old Street and Great Eastern Street fork. Anna