The Dollis Brook Viaduct, also known as the Dollis Road Viaduct, Dollis Viaduct or Mill Hill Viaduct, is a railway

viaduct A viaduct is a specific type of bridge that consists of a series of arches, piers or columns supporting a long elevated railway or road. Typically a viaduct connects two points of roughly equal elevation, allowing direct overpass across a wide v ...

to the west of

Finchley Finchley () is a large district of north London, England, in the London Borough of Barnet. Finchley is on high ground, north of Charing Cross. Nearby districts include: Golders Green, Muswell Hill, Friern Barnet, Whetstone, Mill Hill and H ...

, North London, United Kingdom. It carries the London Underground's Northern line from

Mill Hill East station Mill Hill East is a London Underground station in Mill Hill in the London Borough of Barnet, north London. The station is the terminus and only station of a single-track branch of the Northern line from Finchley Central station and is in Trave ...

Finchley Central station Finchley Central is a London Underground station in the Church End, Finchley, Church End area of Finchley, north London. The station is located on the High Barnet tube station, High Barnet branch of the Northern line, between West Finchley tube ...

. It is the highest point on the London Underground above ground level, reaching nearly . It is located on a branch that was formerly part of the

Edgware, Highgate and London Railway The Edgware, Highgate and London Railway was a railway in North London. The railway was a precursor of parts of London Underground's Northern line and was, in the 1930s the core of an ambitious expansion plan for that line which was thwarted ...

Etymology

The official name of the viaduct is taken from Dollis Brook which it crosses. The brook was marked on an 1877 Ordnance Survey map and the name may have originated from a farm called Dollis, previously in

Hendon Hendon is an urban area in the Borough of Barnet, North-West London northwest of Charing Cross. Hendon was an ancient manor and parish in the county of Middlesex and a former borough, the Municipal Borough of Hendon; it has been part of Great ...

. This was earlier named Dalys in 1563, (the) Doles 1574, Dallys 1584 and in its current form of Dollis in 1822. This probably meant "the portions or shares of land (in the common field)", from the Middle English word dole. The name is not thought to be connected with the area of Dollis Hill, further south. Dollis Hill is thought to mean a "hill associated with a family called Dalley".

History

The viaduct was designed by John Fowler and Walter Brydone, chief engineer for the Great Northern Railway (GNR) from 1855 to 1861. The contractor that built the bridge was Smith, Knight & Co. The viaduct came into use on 22 August 1867 with the opening of the GNR's single-track

line from Finsbury Park to Edgware, via

and Mill Hill, which was authorised by an Act of Parliament in 1862. Dollis Brook Viaduct map

Although built to carry two tracks, the viaduct initially carried only one. Following the construction of a branch northwards from Finchley to Barnet in 1872, the original Edgware route effectively became a branch of the newer line. In the 1920s, the

London and North Eastern Railway The London and North Eastern Railway (LNER) was the second largest (after LMS) of the " Big Four" railway companies created by the Railways Act 1921 in Britain. It operated from 1 January 1923 until nationalisation on 1 January 1948. At th ...

(LNER, successor to the GNR) planned to electrify the line but work was not carried out until the 1930s when the Northern Heights plan led to the doubling and electrification of the lines. This was in preparation for a transfer of the lines to the London Underground for it to form part of the system's Northern line. The start of the Second World War prevented the plans being completed and only the section of the line to Mill Hill East was electrified and reopened in 1941, whilst the High Barnet branch was electrified in 1940. From this point on London Transport trains used only one of the tracks on the Mill Hill branch and the other track was soon lifted. Freight on the line lasted until 1964 when the line west of Mill Hill East was abandoned, leaving the present arrangement.

Length, span and architecture

The viaduct's 13 segmental

arch An arch is a vertical curved structure that spans an elevated space and may or may not support the weight above it, or in case of a horizontal arch like an arch dam, the hydrostatic pressure against it. Arches may be synonymous with vaul ...

es carry it across the valley of the Dollis Brook, and over Dollis Road. Each arch spans at the springer level, and is based on tapered

piers Piers may refer to: * Pier, a raised structure over a body of water * Pier (architecture), an architectural support * Piers (name), a given name and surname (including lists of people with the name) * Piers baronets, two titles, in the baronetages ...

. In each pier there is an opening with an arched soffit and a dished invert. The viaduct is made from brick. It is the highest point on both the Northern line and the highest point on the London Underground above ground level, reaching nearly . It is not, however, the highest altitude on the Underground system, which is near

Amersham Amersham ( ) is a market town and civil parish within the unitary authority of Buckinghamshire, England, in the Chiltern Hills, northwest of central London, from Aylesbury and from High Wycombe. Amersham is part of the London commuter belt. ...

(

Metropolitan line The Metropolitan line, colloquially known as the Met, is a London Underground line between in the City of London and and in Buckinghamshire, with branches to in Hertfordshire and in Hillingdon. Printed in magenta on the tube map, the line i ...

) in the

Chiltern Hills The Chiltern Hills is a chalk escarpment in England. The area, northwest of London, covers stretching from Goring-on-Thames in the southwest to Hitchin in the northeast - across Oxfordshire, Buckinghamshire, Hertfordshire, and Bedfordshire. ...

, at above sea level.

Around the viaduct

Below the viaduct can be found the Dollis Valley Greenwalk, a long-distance footpath between Moat Mount Open Space in Mill Hill and

Hampstead Heath Hampstead Heath (locally known simply as the Heath) is an ancient heath in London, spanning . This grassy public space sits astride a sandy ridge, one of the highest points in London, running from Hampstead to Highgate, which rests on a band o ...

. This is designed to link many green spaces and wildlife corridors along the way and is approximately long. The geology nearby is of London Clay with small amounts of other rock types. An examination in the late 19th century of the railway cutting between Finchley and Hendon station found a large extent of glacial beds and fossils, and these were thought to extend as far northwest as the viaduct.

References

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External links