In 1966, Haslam and his lover at the time, American banking heir James Davison, bought Black Canyon Ranch, near Phoenix, Arizona, for breeding and showing Arabian horses.
His autobiography, Redeeming Features, was published in 2009; in it, he mentions his affairs with numerous individuals, including architect Philip Johnson and photographer Antony Armstrong-Jones (who later married Princess Margaret).
Besides frequently writing reviews for The World of Interiors and The Spectator, Haslam wrote a gossip column for Ritz Newspaper under the pseudonym Paul Parsons, and has been a contributing editor of British Vogue and Tatler for many years.
To celebrate the launch of the new Beaufort Bar at the Savoy in London in November 2010, Haslam performed two nights of cabaret, singing Cole Porter songs to a private audience that included Kate Moss, Jerry Hall and Sir Andrew Lloyd Webber.
In March 2014, Haslam performed cabaret at the Spectrum Ball at the Globe Theatre, hosted by Francis Boulle, to benefit the National Autistic Society.