Every tour of London, whether it addresses the new, the old or both together, features London's architecture as part of a unique urban phenomenon with a partcular urban pattern. This shifts and alters, but its essential nature has remained remarkably resiliant for over a thousand years.

Waterloo Place was the southern termination of John Nash’s famous ‘royal mile’, stretching from the Regents Park down Portland Place and Regent Street to an area of royal palaces (for example, the rather grand Carlton House, home of the Prince of Wales, later Prince Regent, originally stood on this site, and was demolished in 1826). This area – where Buckingham and St James’ Palaces now stand – had been connected with royalty ever since Edward the Confessor built the Palace of Westminster here which was later the home of William the Conqueror (who constructed the Westminster Hall). For 400 years it was the home of the English monarchs, and remained the administrative centre of the kingdom. The Westminster Abbey was also in this area and it thus became a location where monarchy, the court, the church and the two houses of the Commons and the Lords were located. Today, the Westminster area is the heart of British government offices. Because of this history adjacent areas – particularly to the west, around the royal Hyde Park, in what is now Knightsbridge, Kensington and Chelsea – became very fashionable and remain so to this day. Meanwhile, the true historic heart of London lay to the east: the City of London: the trading settlement founded by the Romans in AD50, after they had invaded this island and crossed the Thames at the lowest convenient bridging point, creating what was to later become London Bridge. The fort and settlement created by the Romans was abandoned about 410. By the later C5th the walled settlement had been abandoned, with the later Saxons settling to the west, around what is now Aldwych.

This is another map indicating London's street patterns and the extent of its development during the Civil War, when new defensive walls were constructed. Note the street pattern.

One of the most famous of the seven gaes into London, at Temple Bar, marked its western boundary and was rebuilt by Wren in the 1670s. To this day, the tradition is that the monarch (coming from Westminster) receives permission from the Mayor of the City of London and comes under his protection when passing beyond this point. Temple Bar has now been rebuilt as a feature of the Paternoster scheme just to the north of St Paul's Cathedral.

This map of late Tudor and early Stuart London (i.e. up to about the mid-C17th) clearly shows the extend of the city surrounded by walls built in 1642, The settlement reaches from around London bridge in the east along the Thames toward the area around the Palace of Westminster and the Abbey. Note that most of this is on the north bank of the Thames – then a much wider and slow-flowing river. In effect, Westminster – like Southwark, a place of theatre, brothels and other entertainments – was a satellite of a self-governing trading community. Between these two poles was a string of grand houses along the River Thames and what is now the Strand. The City itself was walled and had seven gates, most demolished before the end of the C18th. London Bridge was built in 1209 and was the only bridge until another was constructed at Blackfriars in 1769.

Westminster Abbey and St Paul's Cathedral epitomise the importance of the two poles of London's urban geography. St Paul's is reputed to be located on the site of a Roman temple dedicated to Diana, but a Christian church was here at about 604. The abbey dedicated to St Peter at Westminster was found at about the same time and was quite substantial by the time Edward the Confessor became king in 1042. Westminster then was a swampy area which also provided a river crossing (described in 785 as 'a terrible place'). Today, these are still the most notable churches in London, representing the power and semi-autonomy of the City of London, and of Westminster. Between these two poles a ceremonial route occasionally emerges: from, for example, the royal palaces, along the Mall and the Strand, to Fleet Street and Ludgate Hill. This parallels the route that was once more easy to take: along the River Thames.

The overwhelming characteristic of Portcullis House – designed as offices for Members of Parliament – is its contextural sensitivity and references: to Barry and Pugin's Palace of Westminster (1858); and, in particular, to Norman Shaw's New Scotland Yard building (1890; now the Norman Shaw Building).