London is probably PD's worst street circuit to date (except George V). Normally they try and encompass famous landmarks with a fun layout, such as New York and Opera Paris. However here it seems they have just tried to link Trafalgar Square and Picadilly Circus with no thought about the layout.
The track needs a 1-2km extension around some wider streets with some straights, while keeping the current track as "London Short", as that would give the track some variety and overtaking points. For example at Pic circus you could go down Picadilly to Hyde Park corner, then up Park lane to Marble arch, then down Oxford Street, and back down Regent Street to Picadilly circus to rejoin the track. The whole thing comes to about 6.5km which is reasonable, try it on google maps.
I never race the London track, though it's alright for time trial. Same goes for Eiger. The best tracks in the game are Suzuka, Fuji, HSR and Daytona in that order.