Under the Freedom of Information Act I am pleased to be able to publish this resource:
You may notice that whenever you see a uniformed police officer on general patrol, they have an epaulette bearing their rank, OCU (operational command unit) and call sign.
The OCU is made up of 2 letters (one letter for some special divisions/operations)
Where I work, mine are SX. In Sunhill

, they have SO.
So when talking about recruitment into the MET and recommending boroughs or talking about boroughs etc., some of us officers may use these 2-letter codes as this is what we know them as.
Here is the full list of codes:
Borough & CodeWestminster CW
Kensington and Chelsea BS
Camden EK
Hammersmith and Fulham FH
Hackney GD
Tower Hamlets HT
Heathrow ID
Waltham Forest JC
Redbridge JI
Havering KD
Newham KF
Barking and Dagenham KG
Lambeth LX
Southwark MD
Islington NI
Lewisham PL
Bromely PY
Harrow QA
Brent QK
Greenwich RG
Bexley RY
Barnet SX
Richmond upon Thames TW
Hounslow TX
Kingston upon Thames VK
Merton VW
Wandworth WW
Ealing XB
Hillingdon XH
Enfield YE
Haringey YR
Croydon ZD
Sutton ZT