The SIS Building at Vauxhall Cross has been the headquarters of the Secret Intelligence Service, popularly known as 'MI6', since 1994 - and quickly became one of London's most recognised buildings, featuring in many movies. Obviously, it is not open to the public and unexpected visitors are discouraged.

From the website of the SIS: "At the Secret Intelligence Service (SIS) – otherwise known as MI6 – our mission is clear. We work secretly overseas, developing foreign contacts and gathering intelligence that helps to make the UK safer and more prosperous. We help the UK identify and exploit opportunities as well as navigate risks to our national security, military effectiveness and economy. We work across the globe to counter terrorism, resolve international conflict and prevent the spread of nuclear and other non-conventional weapons. We are here to help protect the UK’s people, economy and interests."

The cathedral that often gets missed, because everyone tends to flock to Westminster or St Paul's. But Southwark Cathedral is a beautiful oasis of calm and claims to be the earliest Gothic church in London, dating from 1220. Situated adjacent to London Bridge in an area that used to be renowned for its vice, it has a fascinating history and numerous features, including a soaring nave, a wonderful altar screen that dates from the 16th century and several interesting tombs. It became a cathedral in 1905 and its full name is the Cathedral Church of St Saviour and Mary Overie.

Built between 1756-1766 for John, first Earl Spencer, an ancestor of Diana, Princess of Wales, Spencer House is one of the most elegant and sumptuous private residences ever built in London and one of its finest surviving eighteenth-century town houses. Originally designed by John Vardy and James ‘Athenian’ Stuart, Spencer House is still owned (as of 2020) by the Spencer family, but currently leased to a company chaired by Lord Rothschild and has undergone a massive restoration. These days, it is let out for corporate and private functions, including weddings, but also has limited opening to the public.

Image credit - Historic Houses.

Known as the journalists' church, St Brides, just off Fleet Street, is dedicated to a 5th century Irish saint, St Bridget - or St Bride - of Kildare. The fascinating crypt reveals layers of construction, from Roman times onward, and includes a fascinating museum as well as a 14th century chapel, refurbished in modern style. The crypt was not discovered until 1953. The parents of the first white child born in colonial America in 1585 were married in this church. The church was destroyed in the Great Fire of 1666 and was rebuilt by Wren; the spire is the tallest he built - 234 feet - and was the inspiration for the tiered wedding cake. The interior was rebuilt in the 1950s after destruction in World War Two. The Journalists' Altar commemorates journalists from all over the world who have died or been injured during the course of their work.

On the corner of Hart Street and Seething Lane, this is one of the smallest churches in the City of London and one of a handful to survive the Great Fire of 1666 - thanks in this case to the efforts of Sir William Penn (father of the founder of Pennsylvania). It was Samuel Pepys' favourite church - he lived and worked on Seething Lane and is buried, with his wife, under the nave. Some say St Olave's is built on or near the site of the legendary Battle of London Bridge in 1014, in which Olaf II of Norway fought alongside Ethelred the Unready against the Danes. Anyway, the church is dedicated to St Olaf, the patron saint of Norway. It was gutted by bombing during WW2 and restored in 1954. It has some lovely memorials and a fascinating medieval crypt chapel, with a well.