There is a published procedure at NW which is to join downwind, but the problem is that most people ignore it and join straight in or on a right or left base according to which direction they've come from. I know, I used to myself but have tried to be good recently. I wonder if the NW procedure could be revised. During Aerofair the temporary ATC had us joining in the overhead at 1400 and descending into the circuit. This worked OK despite the zillions of aircraft which were joining, and not just because of the (excellent but overworked) ATCOs: most people kept a good lookout and maintained safe spacing. At White Waltham, with Heathrow airspace above the field, an overhead join at 1300 QFE with a deadside descent to 800 feet works just fine. There is, however, more vertical separation from the CAS available at WW, whereas at NW you are pretty close to Stansted's air if in the overhead above the circuit, so it may be that the present system is the best that can be devised.
PS: The R&B procedure is described in the AAIB report on the midair. I take the point that the manouevre performed during that incident was not a standard run and break.
[ 20 July 2001: Message edited by: FNG ]