Soane's first substantial works to the House of Lords were prompted by the accession of the King, George IV, and his desire for a grander Royal Entrance to the Palace of Westminster. The new entrance was to form the final stage of a processional route for the monarch terminating at the King's Robing Room and was to be followed at the annual State Opening of Parliament. Soane's new additions consisted of an arcaded, curved Royal Entrance from Old Palace Yard and a Scala Regia (Royal Staircase) leading to the Prince's Chamber.
Soane's scheme was submitted to the King with the endorsement of Lord Liverpool and Sir Charles Long and approved in April 1822 at an estimated cost of £8,000. Over the following months the plan was altered and designs were made for turning the Prince's Chamber, old House of Lords and Painted Chamber into a Royal Gallery 'to be decorated with paintings, bassi-relievi and statues to perpetuate the glorious achievements of British valour' (SM 71/2/84). In September a porte-cochère was added to the Royal Entrance at the request of the King. Having commenced on 10 August, work was completed by 5 February 1823 at a total cost of £7232 1s 2d.
The Royal Entrance itself was designed by Soane in a Gothic style matching the medieval exteriors of the Palace of Westminster and James Wyatt's much-derided additions to the House of Lords (1806-12). The Scala Regia, though, was built in a richly-ornamented, Soanean style, with domed and vaulted ceilings, top-lighting and Neoclassical motifs, largely derived from engravings in Desgodetz's Les Édifices Antiques de Rome,1682 (see SM 71/2/44). According to Arthur Bolton (curator, 1917-45), 'The Scala Regia was, perhaps, the best of all Soane's designs, and even if it was possibly somewhat gaudy in detail... it is undoubtedly a fine and characteristic composition', although Sir John Summerson was of the opinion that this - and the Royal Gallery - were 'no advance on his very earliest studies'. In his project of 1794-96, Soane had also made designs for a Scala Regia, although it bore little resemblance to the executed staircase.