I was heading west on the M25 on Thursday afternoon, aiming for Wales. Instead of coming off the M25 to join the M4 by Heathrow, the satnav directed me onto the M3, then onto the A322 through Bracknell to join the M4 at J10. I was a bit dubious but followed its advice anyway. The A322 is a slower road, with a number of roundabouts and traffic lights to negotiate, but I wouldn't be surprised if it's genuinely quicker than dealing with the usual congestion around Heathrow.