Ampthill tunnel is a railway

tunnel A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and is usually completely enclosed except for the two portals common at each end, though there may be access and ve ...

Ampthill Ampthill () is a town and civil parishes in England, civil parish in the Central Bedfordshire district of Bedfordshire, England. It lies between Bedford, Bedfordshire, Bedford and Luton. At the 2021 census it had a population of 8,825. Histor ...

on the

Midland Main Line The Midland Main Line (MML), sometimes also spelt Midland Mainline, is a major Rail transport in Great Britain, railway line from London to Sheffield in Yorkshire via the East Midlands. It comprises the lines from London's St Pancras railway ...

, being positioned between

Bedford Bedford is a market town in Bedfordshire, England. At the 2011 Census, the population was 106,940. Bedford is the county town of Bedfordshire and seat of the Borough of Bedford local government district. Bedford was founded at a ford (crossin ...

and

Flitwick Flitwick () is a town and civil parish in Central Bedfordshire, England. It is mentioned in the Domesday Book of 1086 as "a hamlet on the River Flitt". The spelling ''Flytwyk'' appears in 1381. The nearby River Flit runs through Flitwick Moor, ...

. It consists of two separate bores, each one accommodating double-track throughout. The first Ampthill Tunnel was built during the 1860s; growing demand on the line led to the original double-track configuration being inadequate for further growth. Thus, during the 1890s, a second Ampthill Tunnel was constructed directly alongside, facilitating the Midland Railway's expansion plans of running a quadruple-track arrangement between

Kettering Kettering is a market town, market and industrial town, industrial town in the North Northamptonshire district of Northamptonshire, England, west of Cambridge, England, Cambridge, southwest of Peterborough, southeast of Leicester and north- ...

and

London London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...

wherever practical to do so. Both bores have remained active through to the present day. During mid 2012, Ampthill Tunnel was subject to a series of high speed evaluation runs, including a record maximum speed for the route of ; in the following year, the line speeds were increased to 125 mph along much of the Midland Main Line.

History

The Ampthill Tunnel was constructed during the early 1860s on behalf of the

Midland Railway The Midland Railway (MR) was a railway company in the United Kingdom from 1844 in rail transport, 1844. The Midland was one of the largest railway companies in Britain in the early 20th century, and the largest employer in Derby, where it had ...

to convey what would become the

. It was necessary to traverse a hill on the outskirts of the town of

, the summit of which was reported to be above the level of the railway. The local geology that the tunnel was bored through, which largely consisted of

Oxford clay The Oxford Clay (or Oxford Clay Formation) is a Jurassic marine sedimentary rock formation underlying much of southeast England, from as far west as Dorset and as far north as Yorkshire. The Oxford Clay Formation dates to the Jurassic, specific ...

, was found to contain numerous

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s; a number of these were recovered during the excavations for the tunnel and subsequently studied. By the 1890s, company officials had recognised that, due to a lack of free capacity for running further services, an expansion programme was required for the Midland Main Line, which primarily involved its widening from two tracks to four along much of the route between

and

. In accordance with this policy, between June 1893 and 1895, a second Ampthill Tunnel was constructed alongside the first bore. As it was determined to be impracticable to drive a bore between the faces due to the lengthy cuttings on either side for the operating line, the additional tunnel was instead entirely excavated from three shafts that were sunk from above. The completed second tunnel had a length of ; this was slightly shorter than the original tunnel, which reportedly possessed a length of . On 1 July 2012, a new record maximum speed for the Midland Main Line was established by a

British Rail Class 222 The British Rail Class 222 ''Meridian'' is a group of 5- or 7- car diesel-electric multiple-unit high-speed passenger train capable of . Twenty-seven sets were built by Bombardier Transportation in Bruges, Belgium. The Class 222 is part of the ...

diesel multiple unit A diesel multiple unit or DMU is a multiple-unit train powered by on-board diesel engines. A DMU requires no separate locomotive, as the engines are incorporated into one or more of the carriages. Diesel-powered single-unit railcars are also ...

(DMU), which traversed Ampthill Tunnel at a speed of ; the tunnel was closely monitored by engineers to evaluate the effects of the pressure waves generated by the train's speed run. Having found the conditions imposed acceptable, numerous stretches of the line were cleared for trains to regularly run at the elevated maximum speed of 125 mph, including Ampthill Tunnel.

References

External links

{{commons
Ampthill Tunnel on the Midland Mainline via geograph.org.uk

60103 'Flying Scotsman' races out of Ampthill Tunnel on 'The Yorkshireman' - 30/06/18 via youtube.com
Railway tunnels in England Ampthill Midland Railway Rail transport in Bedfordshire Tunnels in Bedfordshire