Mount Pleasant

At the start of the 20th century, Mount Pleasant sorting office was considered to be 'probably the largest sorting office in the world'. A century later, it is still one of the largest and busiest sorting offices in Britain. It is also home to The Royal Mail Archive and the BPMA office.

Early history

Until the 17th century this area was open fields sloping down to the Fleet River. This is presumably why the area became known as 'Mount Pleasant'. The area had a second name: 'Coldbath Fields'. This honoured the Cold Bath Spring which had been discovered in 1697.

In 1794 the Middlesex House of Correction (Clerkenwell Gaol) was built on the site. The penitentiary became known as Coldbath Fields Prison.

The Post Office Takes Over

Coldbath Fields closed as a prison in 1877. On 30 August 1889 the Post Office Sites Act was passed by Parliament. It officially transferred the old prison to the Post Office. The site quickly developed into the principal parcel office and one of the largest buildings in the London postal service.

Postal workers objected to working at 'Coldbath Fields', a name long associated with the feared gaol. As a result the designation 'Mount Pleasant' was formally used from 1888.

Working life in the 19th century

In the late 19th century the development of the Mount Pleasant site was driven by the growth in Britain’s annual parcel traffic. This grew from 22 million when Parcel Post began in 1883, to 43 million in 1891. In December 1891 a local newspaper reported that operating floor space at the Mount was now over 70,000 square feet.

In 1900, the London Letter Post Office transferred to the Mount from St Martins-le-Grand. By 1900, 70,000 parcels and packets were handled at Mount Pleasant each day, with an estimated daily total of 190,000 items over the Christmas period of 1897.

As it entered the 20th century, Mount Pleasant was being referred to as 'probably the largest sorting office in the world'.

The Post Office Underground Railway

A mail rail train being loaded

During the early years of the 20th century operations at the Mount continued to expand – stimulated by a national annual volume of post that had reached a staggering 5.9 billion items by the eve of the First World War.

To avoid London's congested streets, the Post Office decided to travel underneath them. Construction of the Post Office Underground Railway (later known as Mail Rail) began in 1914.

Pre-war expansion

In the inter-war period, the main physical change to the Mount was a new wing, built as a substantial extension to the Letter Office. This aimed to bring an unprecedented degree of mechanisation to postal sorting.

As late as 1917 some of the old prison cells were still being used to store parcels. By 1929 the last of the remaining sections of the prison were demolished to make way for the extension.

In November 1934, the new building was officially opened by the Duke and Duchess of York (the future King George VI and Queen Elizabeth). Over one thousand staff and visitors looked on as the Duchess tried her hand at operating a new stamp-cancelling machine. The ceremony was complete when the Duke operated switches that set in motion the sorting machinery on the ground floor.

Duke and Duchess of York opening the new wing of Mount Pleasant in November, 1934

The Mount under fire: World War II

As early as February 1937, the Post Office began to prepare for a new war. Staff were trained and prepared to take on extra duties so that there would be as little disruption to the mail as possible.

Structural alterations were made to the Post Office Underground Railway so it could be used as an air raid shelter for staff. An auxiliary bomb disposal unit was set up at the Mount. The sorting office roof had been used since 1908 as a shooting range for the Post Office Rifle Club. At the outbreak of war it was given over to more serious pursuits as an air raid warning post was installed.

Air raids devastated a number of buildings in the London Postal Service and Mount Pleasant did not escape. The first major incident occurred on 16 October 1940 when a high-explosive bomb fell on the Farringdon Road entrance to the Parcel Block. The Farringdon Road water main was split. This flooded the Post Office Underground Railway tunnel beneath. 

On 18 June 1943 the Parcel Section was all but destroyed by a single incendiary bomb. The resulting fire was fought for four hours but almost the entire building was gutted, including 77,000 parcels. Two members of staff were killed and a further 34 were injured.

An Air Raid Patrol Roof Spotter at Mount Pleasant in 1945

Post-war reconstruction

At the beginning of 1945 Mount Pleasant was the premises of the Inland Letter Sorting Office, the London Returned Letter Branch and the Headquarters of the Post Office (London) Railway. The site also held

• administration offices,
• the North Postal Engineering Section,
• the Central London Mail Van Garage
• the Supplies Department.

Rebuilding the Parcel Section after the 1943 air raids was just the first step in a comprehensive renovation at the Mount, which was itself part of broader modernising changes in British industry in the post-war era.

The 1954 fire

On 5 October 1954 thousands of employees and large amounts of mail were evacuated from the building when the Supplies Department caught fire at 10.15a.m.

The event caused some controversy when it emerged that over twenty minutes had elapsed between the discovery of the fire and making the emergency call. Ironically, the reason for the hold-up was not negligence but over-preparedness: the Mount had its own firefighting squad to handle small fires and it was only when this team realised they were unable to quell the blaze that the fire brigade were summoned. 

Postcoding

The introduction of postcoding, as intended, drove further postal mechanisation: from 1979 the first fully automatic sorting machines were introduced. The Mount officially became a Mechanised Letter Office (MLO). It was here that the Post Office began trialling Optical Character Recognition (OCR).

OCR reads printed addresses and the machine converts the postcode into a series of phosphor dots which it prints onto the envelope. This allows the sorting machine to 'read' each address automatically from the phosphor dots.