Very funny to see all these dinosaurs claiming that if you don't have an 020 phone number you are not in London.
Nowadays, you can LITERALLY buy a number with the prefix of your choice regardless of where you live.
At the end of the day, London is very clearly defined by a list of 32 boroughs. If you live in any of the following, you live in London, regardless of postcodes, phone numbers or bloody colour of the buses.
These are the boroughs:
Barking and Dagenham, Barnet, Bexley, Brent, Bromley, Camden, Croydon, Ealing, Enfield, Greenwich, Hackney, Hammersmith and Fulham, Haringey, Harrow, Havering, Hillingdon, Hounslow, Islington, Kensington and Chelsea, Kingston upon Thames, Lambeth, Lewisham, Merton, Newham, Redbridge, Richmond upon Thames, Southwark, Sutton, Tower Hamlets, Waltham Forest, Wandsworth, and Westminster.
To that list, you need to add the City of London, which has a very particular status.
This settles the debate.