Yep, I have the book 'Fire In His Soul' by Alan Robertson. It is essential reading.
According to the book, Mingus paid a visit to Harriott as he was literally on his death bed in a Southampton hospital. Apparently he turned up during the night out of visiting hours and had to be turned away. Left a message for Harriott though.
It's also on record that Mingus had huge respect for Harry Beckett, with whom he'd recorded a soundtrack album back in the early 1960s. Harry usually throws in some Mingus material in his live shows to this day.