In July 2014, Stewart launched Hands Across The Border, a project to construct a cairn called 'The Auld Acquaintance' as "a testament to the Union". Built by members of the public, it is close to the Scotland–England border near Gretna. During the run up to the Scottish independence referendum, Stewart said of the project: "We wanted to come up with a lasting marker of our union, something that future generations will look back at and remember, with deep gratitude, the moment we chose to stay together." The campaign received support from several notable public figures in the UK, including actress Joanna Lumley, explorer Sir Ranulph Fiennes, mountaineers Alan Hinkes and Doug Scott, and historians Simon Schama and David Starkey. Approximately 100,000 stones were laid on the cairn, many with personal messages.