Prince William was among the guests at the wedding of Hugh Grosvenor, the Duke of Westminster, and Oliva Henson, at Chester Cathedral.
The pair tied the knot in front of around 400 people, with the Prince of Wales serving as usher, at the event dubbed as the “society wedding of the year”.
Police removed two people from the crowd after orange smoke was deployed from a fire extinguisher-type device as the billionaire aristocrat, 33, and his new bride, 31, left the cathedral.
The Just Stop Oil environmental group said two of its members had set off the orange flare.
Cheshire Police said a 69-year-old woman from Manchester and a 73-year-old woman from Suffolk had been arrested on suspicion of public order offences.
The Duke of Westminster topped the Sunday Times 40 Under 40 Rich List earlier this year, boasting a fortune of £10.1 billion.
A private wedding reception took place at the Grosvenor-owned Eton Estate, just over four miles from the cathedral, where the newlyweds will live.
Harry, the Duke of Sussex, turned down an invitation to the wedding amid tensions with William.
