Ident on departure - LTMA
 

Can anybody tell me why the London TMA ATCOs always ask for an ident, even though passing altitude may be given? Is it something to do with the systems in Swanwick, a habit, or is there a different reason?

Always been intrigued by this, so cheers for any responses!

Even though your callsign is 'automatically' paired with your transponder code, the controller still has to positively identify you by observing you reacting to his instruction to 'squawk ident'.
Do not 'ident' until the controller tells you to.

This was my next query... Brilliant, thanks for the reply.

Interesting, in most other areas, especially in the rest of europe, pilots do not have to ident. Checking in with callsign, altitude passing and cleared altitude (usually the first SID stop altitude) is enough.

It could be they are 'fed' with departure times which they can correlate with the aircraft's label appearing on their displays; this is an alternate way of identifying a departing aircraft provided it is carried out within 1nm of the end of the runway. Departures from LTMA airports often do not make 2 way contact immediately hence it is not done.