As predicted by most on here - Channel 4 are claiming the JM was simply unsuitable for their re-formtting of their racing coverage - it was nothing to do with his age.
Fighting on the 'age' platform was never going to win - it's about the only sure ground Channel 4 can respond from - the truth is, JM is past his time, the viewers and the channel don't want him, so he had to go. His age has nothing to do with it - only to harm his case - in the eyes of the public, most men of his age would be happy to retire with the money he has made, and let a younger presenter take over.