Having spent many hours in the area you are talking about, I can confirm that it is a common occurrence for traffic at the QE2 Bridge legally at 2400ft to get what looks like very close to traffic for LCY which is often crossing that part of the M25 at or descending to 3000 ft prior to intercepting the glide path for the ILS for 28 at LCY. Many is the time I have looked up at a VLM F50 and been able to see the heads in the cockpit windows as it goes overhead. An airliner of any size can look very big from 600 ft (200yds) away, especially on a nice day such as we have had recently. So provided you were on the right QNH and not above 2400ft then it was probably legal. As an ATCO I find it an anomaly that this 600 ft separation is quite legal against traffic outside CAS the intentions of which are not known, whereas we have to provide 1000ft between two aircraft inside CAS, both of which are under our CONTROL.. .. .Whilst not wishing to discourage you from making a report, I would urge you to think carefully whether the surprise by which you were taken might not be colouring your assessment of the separation between you and the Dornier (328 from Scotland, I assume!). Remember that an AIRPROX P is a situation where in the opinion of the pilot the safety of the aircraft was compromised. Was that really the case here, or were you just very surprised at how close he came while still remaining legal? If you are still convinced that your safety was compromised, then file an AIRPROX as already highlighted here.. .. .You might like to compare your experiences with those of the two pilots involved in a VERY close airmiss in the same piece of sky last year. It was recently summarised in either 'Pilot' or 'Flyer'. . .. .If you are flying ANYWHERE around the LL CTR, keep a VERY good lookout, as every b***ger is sandwiched into the airspace beween about 2000 ft and 2400 ft! <img border="0" title="" alt="[Eek!]" src="eek.gif" />