'He had a sense of humour, which no truly intelligent mind can lack'
This sounds like a case of what Anthony Flew in his book Thinking About Thinking labelled 'The No True Scotsman Move'. If someone says 'No Scotsman could commit a gruesome murder' and then is confronted with evidence that someone who was born in Scotland had committed such a murder, they explalin 'Ah, but if they committed a murder like that, they're not a true Scotsman'. Similarly if I manage to dig up some examples of very intelligent people who completely lack a sense of humour, no doubt Anthony Grayling will tell me they are not 'truly intelligent'. Isn't it wishful thinking to believe that a sense of humour should be a necessary constituent of intelligence?