Conservative Party leadership contender David Davis has taken a few jabs at David Cameron.

He has warned Conservatives not to take chances with a leader who is inexperienced - which possibly describes 39-year old Mr Cameron quite well.

And, while Mr Cameron faces uncomfortable questions about his student days, Mr Davis has backed a police crackdown on middle-class drug users (so we working class types can puff to our hearts’ content, then?)

Furthermore, reflecting perhaps that Cameron has been described in the past as ‘Tory Blair’ Mr Davis promised to be “the antidote to Brown, not the heir to Blair”.

I would advise Mr Davis - and I’m sure he reads my blog - to be very careful. Too much of anything that even whiffs of bad-mouthing will turn people away from him. There is an unwritten rule that leadership hopefuls concentrate on promoting themselves rather than doing down their opponents.

Some Conservatives will take a very dim view of anyone who breaks with this tradition…