Mr van Straubenzee, 36, who is the boss at the private office of property firm Knight Frank, married the Duke of Northumberland's daughter Lady Melissa Percy in 2013. Their wedding was held at her family's ancestral home Alnwick Castle, which doubles as Hogwarts in the Harry Potter films. Princes William and Harry were among the guests.
But within three years they split, with Mr van Straubenzee finding love with 31-year old Ms Lanigan-O'Keeffe.
Charity-minded Ms Lanigan-O'Keeffe, whose brother is Irish Olympic pentathlete Arthur Lanigan-O'Keeffe, runs the social action projects for Thomas's schools across London.
The teacher is originally from Co Kilkenny, Ireland, and the barrister Stephen Lanigan-O'Keeffe is her father.
Thomas Alexander van Straubenzee (b 1982 ), scion of that landed family, eldest son of Mr Alexander Henry van Straubenzee (b 1951), by his wife the former Claire S. Fenwick (b 1954)
more about his 1st marriage https://groups.google.com/forum/#!topic/peerage-news/Hpz_dXjSsOg