just to add something to part a The English Heritage website info on the London section of the Landscape Investigation Team says.....

"English Heritage's Landscape Investigation Team carries out research through 'field survey', and field survey needs.... um ... fields! As a result, we have undertaken relatively little research in London (or other major urban areas). In the past, we have examined Central London's Royal Parks, which had previously been almost overlooked by archaeologists. Our investigations encountered everthing (sic) from a pagan Anglo-Saxon cemetery in Greenwich Park....."