Technical answer: Metropolitan services assist you (police, nhs etc), vote for London mayor, in one of the 32 boroughs. But anyone who has been to Sutton or Romford knows it isn’t really London 🤣
Real London is a postcode that begins: N, S, E, and W.
Not places like: Romford, Richmond, Kingston, Bexley, Erith, Bromley, Croydon, Sutton… All the newer bits that are now Greater London boroughs but absolutely don’t feel like London at all. They don’t have a London ethos and are right wing/lacking diversity.
2 insane instances when this was an issue:
A client wanted some stuff sent to their home address. Staff sent to the address provided. Item returned by Royal Mail due to incorrect address. Address provided: “Uxbridge Road, London, WD3”. WD3 is Rickmansworth in Hertfordshire. There is an Uxbridge Road in London postcode W3. Royal Mail had crossed out the “D” and tried to deliver it in Acton (W3), London. Ultimately returned.
Customer furious. Kept on insisting she lived in London because Rickmansworth was on the Metropolitan line 😆
My grandmother had a dementia test. One of the questions she got “wrong” was the doctor asking what part of London she lived in and her insisting she lived in Surrey - she lived in Kew. Post address: Kew, Richmond, Surrey. TW postcode. But the doctor refused to accept her answer and was incredibly condescending about it until I intervened.