For 150 years, it was in Lombard Street, before a new purpose-built headquarters, designed by Robert Smirke, was opened on the eastern side of St. Martin's Le Grand in 1829.

[3] While externally attractive, Smirke's General Post Office suffered over the years from internal shortcomings due to ever-increasing demands on available space.

[6] Elsewhere in the building accommodation was provided for clerks and other members of staff, who were at that time required to live on site owing to the need to be available when the post arrived, by day or by night.

[5] The General Post Office remained in Lombard Street for a century and a half, during which time it continued to expand into neighbouring properties; however the increased employment of mail coaches towards the end of the 18th century caused difficulties as there was very little space for them to pull up and they were forced to queue in the narrow street.

A parcel of land on the east side of St. Martin's Le Grand was chosen; however the clearance and preparation of the densely-occupied site took several years, and it was only in May 1824 that the stones of the new building began to be laid.

Above the main entrance was a large chiming clock (by Vulliamy) with an external and internal dial, which governed timekeeping within the building.

[18] Members of the public could post letters and other items from inside the hall through boxes in the wall, from where they would fall into hoppers and be loaded into trolleys to be taken to the sorting offices beyond.

The room was a hive of activity at the start of the day, when coaches arrived from around the country laden with letters for London; and at the end of the day, when the letters from London were sorted and stamped before being bagged, and loaded on coaches for delivery to provincial post offices all round the country.

Before leaving the building they were placed in the custody of the Mail-Guards, who were armed and accompanied the bags on the coaches to ensure safe delivery.

[12] The London District Office had its own entrance on the east side, by which letter bags were conveyed to and from the waiting mail carts and riding-boys.

Within a decade of the building's opening, rail had replaced road as the principal means of distribution around the country, consigning the mail coach to history.

[16] At around the same time a transit system was installed whereby 'two endless chains, worked by a steam-engine, carry, in rapid succession, a series of shelves, each holding four or five men and their letter-bags, which are thus raised to various parts of the building'.

[16] Reforms undertaken in the 1850s, when the Duke of Argyll was Postmaster General and Rowland Hill was Secretary, helped ease the overcrowding somewhat: the erstwhile separate operations of the Inland, Foreign and London District offices were brought together to form a single Circulation Office, overseen by the Controller of the London Postal Service.

[13] The districts were named according to their compass bearing in relation to St Martin's Le Grand (a nomenclature which is preserved in London's postcode designations).

[8] As part of these alterations a new upper floor was inserted along the double-height length of the hall to provide more space for the sorting of newspapers.

[27] In 1874, a new building, designed by James Williams, was opened on the western side of St. Martin's Le Grand: GPO West.

[23] As well as using wire connections, the CTO was linked to 38 different branch offices around central London using a network of pneumatic tubes (inherited from the Electric Telegraph Company and subsequently expanded).

[33] Meanwhile, in 1880, a new building opened a quarter of a mile to the south in Queen Victoria Street; it initially accommodated the Post Office Central Savings Bank.

The outer arched entrances were topped with sculptural likenesses of two recent Postmasters General: H. C. Raikes (facing St Martin's Le Grand) and Arnold Morley (overlooking King Edward Street); while the equivalent arches on the courtyard side had representations of David Plunket and George Shaw Lefevre (recent First Commissioners of Works).

[30] Meanwhile, Robert Smirke's original General Post Office (which, to avoid confusion, had been renamed GPO East) continued to deal with letters and newspapers.

[39] To enable the rebuilding, the Inland and Newspaper sections of the General Post Office were transferred in 1900 to a new building on the Mount Pleasant site, leaving GPO East to focus on the sorting of London and Foreign correspondence.

[40] (At the same time, double-aperture pillar boxes began to be installed in central London, with one side for 'London and Abroad' and the other for 'Country' letters, in line with these new arrangements).

[41] In 1900, the Central London Railway was opened, with the nearest station to St. Martin's Le Grand being named Post Office.

[2] The intention had been to construct a new 'GPO East' on the site, to accommodate the GPO's still-expanding administrative staff; but although plans were drawn up these never came to fruition, and the land was eventually sold in 1923.

[44] The St Martin's Le Grand area remained a hub for London's postal services well into the second half of the twentieth century.

In the mid-1920s, several steel-framed office blocks were built on the site of Smirke's demolished 'GPO East' by the newly-formed St Martin's Le Grand Property Group, and let (for the most part) to banks and manufacturing firms.

[48] It was damaged by an aerial bomb dropped by a zeppelin during the First World War, which disabled the inland telegraph system for several hours.

A plaque on the side of the BT Centre records that 'From this site Guglielmo Marconi made the first public transmission of wireless signals on 27 July 1896'.

The demolition of Smirke's 1829 General Post Office was not unopposed, and there were moves at the time to salvage the central portico and pediment and rebuild them elsewhere (one suggested location being Shadwell Park).

[2] These ideas came to nought, however,[44] and today one of the only surviving fragments of the building is an Ionic capital from the right-hand side of the portico: this five-ton piece was presented to Walthamstow Urban District Council and is sited in Vestry Road.