As an American who has lived in Britain for the last eight years (my wife is British) I have to agree with Marty; the policy is overly restrictive, out of sync with the rest of the world and IMO has dubious value in protecting any of us from terrorism. And it is not just restricted to Heathrow, it's all UK airports (Luton, Stansted, Gatwick, etc). And while the policy may be "well known" within the UK and parts of Europe, there are plenty of places where it is not. We have had plenty of friends and business colleagues fly into either Heathrow or Gatwick and either be caught-up in this or surprised that it was so restrictive.
It's a problem not just for photographers traveling with expensive gear, but also for business travelers. In the past years, we use to take at least two trips per year to the US, both as holidays to see family and as photo trips to accumulate stock images. We had a back-pack of photo gear each, plus a long lens case each. No more. We haven't done a US photo trip in a year and I doubt that we will until the policy changes (assuming it does

).
Almost as worse is that the carry-on sizes for the "one bag" have changed as well. As I recall, they were changed by the government at least twice in the last year. And at least one airline has a permitted carry on size that is less than the government permitted limit.