The route begins at Marble Arch from its junction on the A40 road in London with Portman Street/Gloucester Place (northbound) and Baker Street/Orchard Street (southbound).
Finchley Road becomes a dual-carriageway through Swiss Cottage and Hendon Way and intersects with the North Circular Road near Brent Cross shopping centre.
The road passes through Hendon and after the junction with the A5150, (close to the Metropolitan Police's police college and the RAF Museum).
The A41 overlaps the A1 at Five Ways Corner with the section known as Watford Way.
It passes through Mill Hill, separating with the A1 at Apex Corner roundabout After crossing the M1, near Elstree, it links the M1 at Junction 4, and then meets the A5 at a roundabout (where the A5 becomes the A5183).
The A41 continues alongside the M1 into Hertfordshire.
This section is known as Elton Way, as far as the roundabout with the B462.

Running parallel to the M1, it intersects with Junction 5, (Berrygrove Interchange).
The road continues north, passing over the River Colne, to the east of Watford, crossing the A412 near Garston at "the Dome roundabout".
After passing under the junction with the A405, the A41 turns towards the west.
At a roundabout, with the A411 to Watford to the south, and the M25 spur straight ahead to join the M25 westbound at junction 19, the A41 continues north through Hunton Bridge crossing the River Gade and the Grand Union Canal to meet the M25 at junction 20.
The old route through Kings Langley is now classified A4251.
The route begins at Marble Arch from its junction on the A40 road in London with Portman Street/Gloucester Place (northbound) and Baker Street/Orchard Street (southbound). Finchley Road becomes a dual-carriageway through Swiss Cottage and Hendon Way and intersects with the North Circular Road near Brent Cross shopping centre. The road passes through Hendon and after the junction with the A5150, (close to the Metropolitan Police's police college and the RAF Museum). The A41 overlaps the A1 at Five Ways Corner with the section known as Watford Way. It passes through Mill Hill, separating with the A1 at Apex Corner roundabout After crossing the M1, near Elstree, it links the M1 at Junction 4, and then meets the A5 at a roundabout (where the A5 becomes the A5183). The A41 continues alongside the M1 into Hertfordshire. This section is known as Elton Way, as far as the roundabout with the B462.
Running parallel to the M1, it intersects with Junction 5, (Berrygrove Interchange). The road continues north, passing over the River Colne, to the east of Watford, crossing the A412 near Garston at "the Dome roundabout". After passing under the junction with the A405, the A41 turns towards the west. At a roundabout, with the A411 to Watford to the south, and the M25 spur straight ahead to join the M25 westbound at junction 19, the A41 continues north through Hunton Bridge crossing the River Gade and the Grand Union Canal to meet the M25 at junction 20. The old route through Kings Langley is now classified A4251.
A41 road