The London Monogram

This was apparently a symbol for London that was in use during the reign of Alfred the Great. Here are some pictures of coins with it on.

I think it'd make a rather fine symbol for London today.

While i'm at it, does anyone know when, where and with whom the use of 'LDN' to mean London originates? It's in some Dizzee Rascal lyrics, and went mainstream(er) with Lily Allen, and seems to have come from the UK garage community, but details would be good. Must check the OED ...