Ok.....I flew through LHR 4 days ago. I brought with me my usual briefcase and my usual "purse" - a small shoulder-thing that contains my travel-wallet and cellphone. And, a coat, which I was wearing.

The purse is tiny and the laptop about 1/2 of the allowed size, yet they still gave me heat for it at security, insisting that I go check it. I looked around on all those with oversized carry-on that went through without problems, and realizing that logic wasn't going to get me anywhere, I asked:

me: so if the content of my purse was in my briefcase, it could go through?
BAA-weenie no. 1: Yes
me: and if it was in the pockets of my coat, it could go through?
BAA-weenie no. 1: yes
me: Thank you

And there and then I loaded the two cellphones from my purse into my left pocket, folded the purse with the travel-wallet into my right pocket (which now was over-filled) and walked past BAA-weenie no. 1 to security.

Shoe-circus was enforced, so I kindly asked if they had foot-protectors since the floor was less than hygenic.
Another BAA-weenie no 2 barfed at me "Sir, you must understand that this is a security operation, and it is for YOUR safety". I took off my shoes and put them in a tray, only to have BAA-weenie no 2 yell at me again that shoes do not go in the trays. I sighed, and went through the WTMD, which of course went off.

After waiting for a lengthy personal secondary, I got to wait for my carry-on to get a very careful and lengthy secondary (!), before I was let go - 5 min past boarding time of my aircraft. The whole thing through security took >1h, and I got the distinct feeling that the BAA-weenies were purposely trying to make me miss my plane -- which, fortunately, was late so I made it.

The morale of the story: LHR and BAA is as bad as -- if not worse than -- the TSA. And, I wouldn't want to bet on taking anything but a single carry-on-item past any BAA port.