Indeed it must have been some years ago. In the last 2 years I've been through LHR approx 300 times, with 2 bags. I've never been challenged or approached about it in Heathrow, and only once elsewhere (Turnhouse).

One bag is a sports rucksack for my 2 laptops, Kindle and liquids (so everything comes out of that bag for Security), the other is a wonderful Skypak floppy 55 cm holdall with everything else. I never check in bags, since the Skypak, which conforms even to Ryanair's view of the baggage world, is quite sufficient for 2 or 3 weeks away from home. I carry these bags rather than wheel them, and they look small compared to the rather sturdy rollerbags to which the rest of frequent-flyerdom seems wedded. Because they are both non rigid bags they are relatively easy to squeeze into the overhead lockers.