After crossing The Bishops Avenue, the A1 becomes Lyttelton Road, which was laid out in 1931 as part of the residential development of the area, and runs east–west along the northern foot of Highgate Hill between Hampstead Garden Suburb and East Finchley.
It is for the most part residential; on the northern side stands the Belvedere Court block of flats.
Built with the road in the 1930s, the building is now Grade II Listed as an example of 1930s architecture.

After passing playing fields to the south, the A1 briefly becomes Market Place, a former street market that has evolved into a short stretch of shops, then becomes Falloden Way – built between 1914 and 1924 as part of a programme of planned extensions to Hampstead Garden Suburb, and runs on an embankment due to a dip in the ground caused by Mutton Brook, a tributary of the River Brent, which runs parallel to the road immediately to the south for its entire length.
The north side of the road is occupied by 1930s housing blocks, whilst the southern side is occupied by a narrow strip of parkland following the brook, and by the northern tip of Big Wood and Little Wood – two of the few surviving remnants of the ancient woodland that once covered what is now north London.


The A1 merges with the North Circular Road (A406) and the two routes run briefly together, crossing over the Henlys Corner interchange.
Henlys Corner is a junction with the 1820s turnpike road, Finchley Road, which was built to provide a by-pass to the route north from London through Hampstead; the name changes to Regents Park Road on the northern, Finchley, side of the junction.
The junction had an £8 million upgrade completed in January 2012, which included Britain's first "hands-free" pedestrian crossing to allow Orthodox Jews to reach the nearby Finchley Synagogue, one of Europe's largest, without operating machinery on the Sabbath.
While a synagogue has stood on the site since 1935, the current building dates from 1967.


After the Henlys Corner interchange, the routes diverge, with the A406 going south to Brent Cross, while the A1 turns north-west as Great North Way through the leafy suburbs of Mill Hill and Hendon.
Great North Way, built in 1926, joins Watford Way carrying the A41, completed in 1927, at Fiveways Corner, and in 1970 a junction with the M1 motorway was created.
The A41 and A1 continue together as Watford Way via Mill Hill Circus to Apex Corner, where they separate, with the A41 turning west, and the A1 turning to run straight north.
After passing Apex Corner, the A1 runs north and out of London as the dual carriageway Barnet Way / Barnet Bypass.
This dual carriageway was part of a 1920–4 road improvement programme that was mentioned in parliament in 1928 as hopefully being completed by the end of that summer.

The northbound carriageway passes the entrance to Scratchwood, an area of ancient forest which is now a local nature reserve, then crosses the A411 from Watford to Barnet at the Stirling Corner roundabout.
A 0.6 miles (0.97 km) proposed link road at this roundabout, estimated at £22.8m in 1987, would have provided access to the M1, but the plans were subsequently abandoned.
The link had been planned during discussions for the Hendon Urban Motorway, which was intended to carry the M1 all the way down to Hyde Park Corner as part of the London Ringways scheme; the interchange would have been junction 3 on the motorway; which is currently the unnumbered junction for London Gateway services.

Past Stirling Corner, the A1 skirts Borehamwood, before turning northeast and running through open countryside to Bignell's Corner.
At Bignell's Corner the A1 crosses under the M25 motorway at a large roundabout near South Mimms services.
North of Bignell's Corner the A1 becomes the A1(M) motorway for a while, and follows the Great North Road route, running north to Edinburgh.
After crossing The Bishops Avenue, the A1 becomes Lyttelton Road, which was laid out in 1931 as part of the residential development of the area, and runs east–west along the northern foot of Highgate Hill between Hampstead Garden Suburb and East Finchley. It is for the most part residential; on the northern side stands the Belvedere Court block of flats. Built with the road in the 1930s, the building is now Grade II Listed as an example of 1930s architecture.
After passing playing fields to the south, the A1 briefly becomes Market Place, a former street market that has evolved into a short stretch of shops, then becomes Falloden Way – built between 1914 and 1924 as part of a programme of planned extensions to Hampstead Garden Suburb, and runs on an embankment due to a dip in the ground caused by Mutton Brook, a tributary of the River Brent, which runs parallel to the road immediately to the south for its entire length. The north side of the road is occupied by 1930s housing blocks, whilst the southern side is occupied by a narrow strip of parkland following the brook, and by the northern tip of Big Wood and Little Wood – two of the few surviving remnants of the ancient woodland that once covered what is now north London.

The A1 merges with the North Circular Road (A406) and the two routes run briefly together, crossing over the Henlys Corner interchange. Henlys Corner is a junction with the 1820s turnpike road, Finchley Road, which was built to provide a by-pass to the route north from London through Hampstead; the name changes to Regents Park Road on the northern, Finchley, side of the junction. The junction had an £8 million upgrade completed in January 2012, which included Britain's first "hands-free" pedestrian crossing to allow Orthodox Jews to reach the nearby Finchley Synagogue, one of Europe's largest, without operating machinery on the Sabbath. While a synagogue has stood on the site since 1935, the current building dates from 1967.

After the Henlys Corner interchange, the routes diverge, with the A406 going south to Brent Cross, while the A1 turns north-west as Great North Way through the leafy suburbs of Mill Hill and Hendon. Great North Way, built in 1926, joins Watford Way carrying the A41, completed in 1927, at Fiveways Corner, and in 1970 a junction with the M1 motorway was created. The A41 and A1 continue together as Watford Way via Mill Hill Circus to Apex Corner, where they separate, with the A41 turning west, and the A1 turning to run straight north. After passing Apex Corner, the A1 runs north and out of London as the dual carriageway Barnet Way / Barnet Bypass. This dual carriageway was part of a 1920–4 road improvement programme that was mentioned in parliament in 1928 as hopefully being completed by the end of that summer.
The northbound carriageway passes the entrance to Scratchwood, an area of ancient forest which is now a local nature reserve, then crosses the A411 from Watford to Barnet at the Stirling Corner roundabout. A 0.6 miles (0.97 km) proposed link road at this roundabout, estimated at £22.8m in 1987, would have provided access to the M1, but the plans were subsequently abandoned. The link had been planned during discussions for the Hendon Urban Motorway, which was intended to carry the M1 all the way down to Hyde Park Corner as part of the London Ringways scheme; the interchange would have been junction 3 on the motorway; which is currently the unnumbered junction for London Gateway services.
Past Stirling Corner, the A1 skirts Borehamwood, before turning northeast and running through open countryside to Bignell's Corner. At Bignell's Corner the A1 crosses under the M25 motorway at a large roundabout near South Mimms services. North of Bignell's Corner the A1 becomes the A1(M) motorway for a while, and follows the Great North Road route, running north to Edinburgh.
A1 in London