Westminster & South Bank Walk

Welcome to London! We're starting in Trafalgar Square, named for the Battle of Trafalgar, the British naval victory over France and Spain on 21 October 1805. This spot has mattered since the 1200s, because distances from London are measured from Charing Cross, right here. The royal stables, the King's Mews, once stood on this site, until George the Fourth moved them to Buckingham Palace and John Nash began redeveloping the area.

The square finally opened in 1844. In the centre is Nelson's Column, 169 feet tall, honouring Vice-Admiral Horatio Nelson, who commanded the fleet at Trafalgar. His statue stands at the top, and four bronze lions by Sir Edwin Landseer guard the base. The National Gallery lines the north side, with St Martin-in-the-Fields to the east.

Look for the fourth plinth, which since 1999 has displayed a changing series of artworks. Every Christmas since 1947, Norway has given the square a Christmas tree. And this has long been a place for protest, from Bloody Sunday in 1887 to modern climate campaigns.

This is Horse Guards, built in the mid-18th century as barracks and stables for the Household Cavalry. It once formed the entrance to the Palace of Whitehall, and later St James's Palace, which is why the King's Life Guard still ceremonially defends it. Between the early 18th century and 1858, this building and the one before it were the main military headquarters of the British Empire. The first Horse Guards was commissioned by Charles the Second in 1663.

When it began to fall apart, with falling masonry said to endanger the sentries, George the Second commissioned this Palladian building from the architect William Kent. Look at the arch in the middle. It leads through to Horse Guards Parade and St James's Park. Only the monarch may drive through it without a special pass.

Two mounted sentries guard the Whitehall entrance from 10 in the morning until 4 in the afternoon, changing every hour, and the Changing of the King's Life Guard takes place on the parade ground behind. Part of the building houses the Household Cavalry Museum.