The 93-year-old bridegroom, meanwhile, was dapper in a sober grey suit with a gold tie, and a pair of thick-soled trainers that were perhaps chosen with comfort in mind.
The pair have yet to confirm a relationship, but were first spotted together just four months after the tycoon broke off his engagement to dental hygienist turned radio host Ann Lesley Smith.
ANDREW NEIL: This brotherly rivalry will be bloody. James (right) and Lachlan (left) have not spoken for years. They refuse to be in the same room. Even meeting over Zoom is near-impossible