It is a dangerous road, no question, but not so dangerous if you have a plan. And I have a plan, and it's a good 'un. I first worked this out on the A40 which was my route in to London when I lived in Buckinghamshire. You simply have to stack the buggers up behind you. Riding in the gutter, particularly in the underpasses on the A3 round Tolworth would be kind of daft. Further south the lanes broaden, and you're better off sticking to the white line because you can't stack them up - they just go round at 70
I pass on the A12, though. Two narrow lanes each way with artics bombing down to Felixstowe. If one is overtaking another there is simply nowhere to go..........
It is possible to take group rides on this type of A road if you have someone at the back who is prepared to adopt the same tactic, but it's understandably not popular. The FNRttC has gone down the A3 at night, but we didn't attempt to jump the M25 junction.