The friendship between the architect Sir John Vanbrugh (1664–1726) and his distant relative Robert Bertie, Lord Willoughby d’Eresby and successively 4th Earl and 1st Marquess of Lindsey and 1st Duke of Ancaster (1660–1723), is firmly but sporadically documented. It appears to have developed during the 1680s, well before Vanbrugh turned to architecture and at a time when, having relinquished a post in the Earl of Huntingdon’s Regiment of Foot, he turned to his kinsmen to seek advancement. On Vanbrugh’s own admission he was highly regarded by Bertie for in a letter written 26 August 1692, referring to events of 1688, he stated, ‘I had been at the Hague in my Lord Willoughby’s Company; That I was his relation, and that (as he was pleased to say) I lead all the Bertue [Bertie] family which way I would’. The letter was written whilst Vanbrugh was a prisoner in the Bastille, Paris, to which he had been committed that year. This was consequent on his visit to the Hague and the subsequent limitation of his liberty at Calais and Vincennes, for the reason that he had been speaking something in favour of the enterprise that the king (William III) was then on the point of executing — that is, war between France and Holland. Like Bertie, Vanbrugh was staunchly Whig. The friendship flourished and appears to have strengthened into a high family regard. In 1711 Vanbrugh was a signatory to the marriage contract of Peregrine Bertie, son of Robert and later 2nd Duke of Ancaster; and in 1719 he was appointed a trustee of the 1st Duke’s will drawn up on 23 May that year. In October 1722 that nobleman became godfather to the architect’s second son, John. The friendship naturally extended to another of the Duke’s family: Robert’s brother, Peregrine Bertie (d. 1711), Vice-Chamberlain of the household from 1694, was said to be ‘Mr Vanbrugh’s intimate friend’.