He wasn't demoted, he resigned from his post, there is a difference.
This is what he said in the Sunday Times:
Me: "Please open the gates"
Police: "No. Please get off your bike and leave by the pedestian exit."
Me: "Please open the gates, I am the chief whip; I work here at N0 9."
Police: No, "you have to get off your bike and wheel it out."
Me: "Look, I have already been in and out several times today. Please open the gates."
Police: "no"
Then he says he did as he was told and:
As I did so, I muttered - though not directly at him - "I thought you guys were supposed to f*** help us". To which the policeman responded "If you swear at me I will arrest you". Then he left.
He also says that at the meeting with the Police Federation, after which they told the press that he wouldn't tell them what he said, a recording of the whole proceedings was made which proves he did tell them what he said. I don't think he would have said that if it were not true as it is so easily provable.
It does seem to have been a bit of a stitch up whish would not be the first time for soem of our police.
Time will tell.