Romance at the Ailsa
The element of the romantic Ailsa story with a basis in fact is the underground passage. The following explanation is borrowed from the Thames Discovery website, www.thamesdiscovery.org (FROG blog - Subterranean Isleworth Part 1), as it tells the basic story perfectly. I have added some relevant (to the pub and local history) facts which are distinguished by [ ] brackets.
Francis Jack Needham (Black Jack), the Second Earl of Kilmorey, [known as Viscount Newry (he was elected to Parliament as member for Newry in 1819)] purchased St Margarets House in 1851 and soon after bought Gordon House, where he resided. He had St Margarets House rebuilt in 1852 [and called it Kilmorey House].
The Earl had separated from his wife, and had taken up with Priscilla, the youngest daughter of a personal friend, Captain William Hoste. [William Hoste had died when Priscilla was five and Needham had become her guardian. When she was twenty and he was in his fifties, they eloped to France, causing a great scandal. They had a son, Charles, who Needham acknowledged was the 'apple of his eye'].
After 1851, she [Priscilla] became terminally ill and died on 21st October 1854. Whilst she was ill, he requested that a family mausoleum be built in Brompton Cemetery, which was finally granted and built in Egyptian style. The Mausoleum was relocated from Brompton Cemetery when he moved his home to Woburn Park near Weybridge in 1862.
In 1868 he returned back to Gordon House and brought the Mausoleum with him, to its final site on a plot of land adjacent to Richmond Road. He apparently had a tunnel built to access the Mausoleum from Gordon House.
Jack Needham was somewhat eccentric, and it is said that he instructed his aides to push him, clothed in his shroud, in his coffin from Gordon House through the tunnel to his proposed final place of rest at the Mausoleum. This bizarre habit was carried out on a regular basis so that he could experience the final route of his own funeral. [Jack and Priscilla remain in the Mausoleum to this day and would love you to visit!]
However, all accounts suggest that although eccentric in a nice way he was overall a good, kind chap. He often arranged treats for his servants, such as going to the theatre, where they all attended as a group and sat together.
Does the underground passage exist?
From research at Richmond Local Studies Department at Richmond Library, the following was revealed: Local residents had never seen the tunnel - even by people who had still been alive only a few years after the funeral.
In 1966, extensive investigations of the Mausoleum floor and gardens were carried out together with excavations. The same was carried out in Gordon House Cellars and surrounding grounds.
The final piece of the jigsaw was established after local council records were discovered during the construction of a sewer in the 1880s, which presumably located the tunnel. The tunnel was seen to be bricked up.
The route ran under what is now Kilmorey Road, [formerly the driveway to Kilmorey house] thus linking Gordon House grounds with the Mausoleum garden. A sloping pathway ran down to the tunnel at either end. The tunnel itself was plastered and painted with a green trellis design.