Kerb Crawling for History

Despite some strange looks, I've been studying the pavement outside the east end of Westminster Abbey recently.  We know that in 1834 there was a street plug (ie access to underground fire mains) in "Speaker's Corner", which was the name for the outside area between the apse of Henry VII's chapel and the Chapter House (as well as the better known area inside).  I'm wondering if the water main still flows along the same route and this manhole cover is the current day access to it - signalled by the yellow fire hydrant sign.  A tad nerdy maybe...?