Prof Ged Martin looks at the history of one of our main transport routes to and from the city

If you catch a train from Harold Wood or Gidea Park or Romford, you probably take the Liverpool Street line for granted.

But it's long been one of Britain's busiest railways, a transport artery of world significance.

The Eastern Counties Railway was opened to Romford in 1839, extended to Brentwood in 1840, and to Chelmsford and Colchester in 1843. By 1851, the line continued through Ipswich to Norwich.

Poorly managed, in 1862 it was merged into the Great Eastern Railway (GER), which served Essex and East Anglia. The energetic GER soon opened new stations such as Harold Wood (1868) and Chadwell Heath (1873), plus a new terminus at Liverpool Street, in 1874-5.

Although a second line, via Cambridge, also served East Anglia, huge amounts of traffic flowed through Romford and Stratford.

Branch lines also fed in freight and passengers.

Braintree was reached in 1848, Clacton in 1882 and Southend, through the Shenfield branch line in 1889. A suburban route from Stratford to Epping and Ongar is now part of the Central Line.

In the 1850s, the Barking Creek fishing fleet, which supplied London, mostly relocated to Great Yarmouth, closer to North Sea fishing grounds. Their catch now went to Billingsgate by rail.

In 1883, the GER opened Parkeston Quay, a new port on the Stour estuary near Harwich. The 600-yard quay was extended in 1911 and 1934.

Luxury "boat trains" delivered passengers to the Hook of Holland ferry.

Freight was equally important. In 1906, 1,300 steamers docked at Parkeston Quay from the Netherlands, Belgium and Denmark alone. Much of their cargo clanked on to Stratford and Liverpool Street.

As goods traffic increased, so too did pressure from commuters. Ilford grew from 8,000 people in 1881 to 41,000 twenty years later, its City workers entirely depending upon GER services to London.

In 1839, 14 trains had run through Ilford each day. By 1876, the average daily number was around 90.

In 1900, there were 450 trains a day in winter. The GER marketed seaside excursion tickets, increasing the number to 520 in summer.

In 1913, it was claimed that the Liverpool Street line was the only railway in the world to operate day and night.

There were four solutions to the increasing congestion.

In 1903, the GER opened its Fairlop loop line, now absorbed by the Central Line. The loop branched off the main line between Ilford and Seven Kings, curving back to join the Epping line near Woodford.

Suburban development was not a priority: Hainault was not built up until after the Second World War.

The Fairlop loop allowed the GER to divert goods trains, around the clock, on a roundabout route to the freight yards at Stratford, thus taking pressure off the main line approaching London.

Sidings were built near Seven Kings for goods trains to wait their turn to Fairlop. They're now the Ilford depot.

Remarkably, the Liverpool Street line mostly operated with just two tracks, one up and one down. A breakdown caused chaos.

Double-tracking each way made it possible to separate fast and slow trains. The process was completed in stages, to Seven Kings by 1899, but to Shenfield only in 1934.

A third solution was to transfer some suburban lines to the London Underground. In 1946, the Central Line (which had terminated at Liverpool Street) was extended to Stratford.

A short tunnel to Leyton annexed the line to Epping. Another tunnel, from Leytonstone to Newbury Park, turned the Fairlop loop into the Central Line's Hainault branch.

The line between Seven Kings and Newbury Park was closed in 1956. It's now allotments.

The final solution to relieve pressure was electrification, which allowed more trains. Electric trains ran to Shenfield from 1949, although Norwich was only reached in 1986.

Now the Elizabeth Line promises a new future for one of Britain's busiest transport routes.