Monckton was a close friend to the late Princess of Wales.
Diana was also the godmother to Monckton's daughter, Domenica, who was born with Down syndrome in 1995.
Monckton has revealed that Diana always provided the ultimate support to Monckton and her daughter, attending medical appointments and always remaining by their sides.
Speaking to PEOPLE in 2016, Monckton said, '[Diana] said, 'Believe in her, love her and I'll be there every step of the way.' She already had that vision of what Domenica could become, which I simply couldn't see.'