He turned down the chance to go on the 1984 England rugby union tour of South Africa, because of his opposition to apartheid.
[citation needed] On 18 February 2007 Knibbs was also named in The Sunday Times top 10 centres of time[verification needed] along with names such as Brian O'Driscoll and Simon Halliday by Bath rival Jeremy Guscott who described Knibbs as being "silky and absolutely superb" and whom admitted it was a "crying shame he never won an England cap".
On 22 March 2016 Knibbs was a victim of attempted murder by transgender fell runner Lauren Jeska.
Knibbs was stabbed several times in the head and neck by Jeska in a "premeditated and savage attack" at Alexander Stadium, in Birmingham.
The attack occurred in the context of a planned review of Jeska's status as a female athlete because she was a transgender woman.