Thanks for all the advice. I think setting off at 7am, or slightly
before, and go by the A12, M11, M25. It does over double the distance
(start N1 3DS), but it ought to be more dependable.

Thanks chaps - if it were just me going, I'd be on the train with hand
luggage... damn the wife!

Some belated comments.

Starting from there, the M11 and Dartford crossing seem somewhat
bizarre.

I live near the Blackwall Tunnel Northern Approach and, if I had noticed
your thread sooner, would have suggested you monitor that this morning
with the web cams ( eg
http://www.tfl.gov.uk/tfl/livetravel...d/default.asp). As
others have said, it is nothing like as bad as it used to be in the days
of tidal flow. And you have the option of bailing out to the M25 via
the A11 if you were to find Blackwall closed. As it is, if you arrive
to find an accident on the QE2 bridge your options are rather limited
(unless scuba gear allows you to snorkel the car).

I would also have supported the suggestion of switching to the A20 from
the A2 (in my experience best done by going via Kidbrooke so as to avoid
the South Circular).

Finally, it's some years since I drove to work daily from Hackney to
Westminster but there was then a massive difference in traffic between
6:00 and 7:00. I don't know if the same true is now but in your shoes
(flippers???) I'd leave at 06:00, count it as a bonus if I arrived at
Gatwick by 08:00 and then treat myself to a good breakfast/brunch.
--
R