How about Charles Barry (jnr) for whom the road I dwell is named? although I don't know if he lived here. Michael Faraday, Henry Bessemer, Camille Pissaro, Margaret Thatcher were all involved with ED, but lived close by (Walworth, Camberwell, Crystal Palace, Dulwich). I'm not sure that Dickens ever lived here (mainly Bankside), but his involvement was more with Dulwich Village and the gallery. Maybe the most important name is Edward Alleyn, who also lived at Bankside but moved to Dulwich (not East Dulwich specifically). None of this ranting answers the question and perhaps "The most important (deceased) person associated with East Dulwich" surely was the bloke with all the dogs on a hill separating us from Camberwell and the Jenny's (Eclair and Agutter).