M25 J21A Bricket Wood Interchange

Layout and signage

Watford
Harrow
A405
London (NW)
(M1 S Link)
  A405


    A405


  St Albans
A405
London (NW)
(M1 S Link)

Lane configuration

LanesLanesLanesLanesLanesLanes

  • Lane 1 exits and does not return.
  • Lane 2 continues ahead.
  • Lane 3 continues ahead.
  • Lane 4 continues ahead.

LanesLanesLanesLanesLanesLanes

  • Lane 1 is gained from the entry sliproad.
  • Lane 2 continues, with option to exit.
  • Lane 3 continues ahead.
  • Lane 4 continues ahead.

Other events

  • Signs Variable Speed Limits apply
  • Signs Variable Speed Limits apply

In this section

What's new

A bridge under troubled bridges

A bridge that was ruined by another bridge, and a type of highway planning beyond any of the UK’s worst nightmares.

The monster seen from below

What might it have been like to stand in one spot and witness the arrival, and the uncertainty, of plans for an urban motorway in West London?

The road that made no sense

It was the UK's only single-carriageway motorway, and twenty years ago it ceased to exist. This is the story of the strange fascination it held, and of my place in history.

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Sir James Drake

County Surveyor and Bridgemaster for Lancashire in the 1950s and 60s, Drake was instrumental in the motorway revolution.

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