“They are very happy and have been going out for some months now. It's a serious relationship," one of the couple's friends had said in April.
Lucy Lanigan-O'Keeffe teaches outdoor learning and mindfulness at one of the four Thomas's schools in London, where Princess Charlotte will begin in September.
According to the Daily Star, Lanigan O-Keefe is the sister of Irish Olympic Pentathlete Arthure Lanigan-O'Keefe.
Lucy is reported to be a 'charity-minded person,' and is in charge of the social action projects at Thomas' Battersea.
Thomas van Straubenzee is the manager of property firm Knight Frank, and was previously married to the Duke of Northumberland's daughter Lady Melissa Percy in 2013.
Prince William and Prince Harry attended the wedding, however, the couple were divorced within three years.
They attended Ludgrove School with them in Berkshire and are as close as brothers.
Prince Harry was best man at Charlie van Straubenzee's wedding to Daisy Jenks, in 2018.
Charlie is even expected to be named godfather to Prince Harry and Meghan Markle's first child Archie Harrison Mountbatten-Windsor, in his upcoming christening in July.
Despite Charlie appearing to be closer to Harry, Thomas is also very good friends with William.