Like Putney Vale, East Finchley (a.k.a. St. Marylebone Cemetery) ought to be on the list of "must-visit cemeteries" much more often than it is. Opened in 1854 to serve the affluent suburbs of Marylebone, Highgate and Hampstead, it has more spectacular memorials than you'd normally expect in a suburban cemetery, and is well worth a visit.
Don't miss the gorgeous bronzes. You'll pass Sir Peter Nicol Russell's tomb on the way in: a young engineer being lifted to heaven by an angel, with a bust of Sir Peter himself on a pillar above them*. This was designed by Sir Edgar MacKennal, who subsequently designed the effigies of Edward VII and Queen Alexandra in St. George's Chapel. Two more bronzes are facing each other, towards the north-west of the main chapel, on the graves of Thomas Tate (a reclining youth pointing to heaven), and Harry Ripley (a mourning woman).
Not all the graves in this cemetery have faired so well. That of Thomas Skarrett Hall, an "Australian colonist" was apparently modelled on the tomb of Napoleon. The enormous pink granite sarcophagus once had a bronze angel seated at each corner, but those were stolen in 1989. The "chapel" at the centre of the cemetery, in fact a mausoleum for Lord Borthwick, owner of The Morning Post, is currently sealed off with railings; there doesn't appear to be any work going on, so I don't know if this is due to decay, vandalism, or simply a preventative measure. Elsewhere, several grave markers have been laid flat, and one huge pink and grey granite slab has been left fallen and cracked.
But in general, East Finchley cemetery is immaculately maintained, and there was an attendant available on the hour to assist mourners (meet him at the main chapel). It seems Westminster Council, who now run this cemetery, are making up for the sins of their past, when East Finchley was one of the cemeteries they sold off for 5p each. Bought back later at a much-inflated price, not all of the cemetery ground could be recovered, leading to the slightly odd sight of a garden centre stuck behind Victorian cemetery railings.
I'm putting this on my "must go back to" list, as the sun was too glaring for much of the time I was there.
Visiting: Walkable from East Finchley tube station. The 143 bus stops right outside, or take the 382 to Squire's Lane and walk round the corner.
* Darren Beach implies that these are two separate monuments "close by" one another, but no one who's actually seen it could think that.