What you'll find is that any radar equipped ATC unit has a block of squawks reserved that they can assign on an ad-hoc basis to traffic. Typically this is done for VFR transits through controlled airspace. Blocks of adjacent units obviously do not overlap, so if the traffic of one unit strays into the airspace of another, the controllers can instantly communicate with each other and resolve the situation.

What makes the 1177 squawk a bit special is that London Info, by default, is not a radar equipped unit (although I recall that they do have access to radar pictures if necessary). The confusion here is that a lot of (foreign) pilots, when given a squawk, automatically assume that they are radar identified and actually receiving some sort of radar-based separation service. Which is totally not the case with London Info. The squawk 1177 is only there to let other units know that this aircraft is handled by London Info, nothing more, nothing less.

Well said backpacker. Scottish Info use 7401 in the same way as London use 1177. There are other "conspicuity codes" too, like 7010 for traffic operating in the circuit. There is a list of all the UK allocated squawks in this part of the AIP: http://www.nats-uk.ead-it.com/aip/cu...ENR_1_6_en.pdf (It also has details of the ATSOCAS etc.)