Bob Ainsworth enjoying the freedom of the back benches

Bob Ainsworth is enjoying the freedom of the back benches

"You have to make the compromise: resign, stay out of the government and you can say what you like... but no one has to do anything about it."

He began in the Whips' Office and finished up in the Cabinet as Secretary of State for Defence.

The MP for Coventry North East, Bob Ainsworth, is one the handful of Labour MPs who served in government throughout the party's 13 years in power.

So there can be few politicians better qualified to explain the pains and pleasures of being in office compared with what we Westminster watchers call "the freedom of the back benches".

'Disastrous' policies?

Before moving to the MoD, he spent two years at the Home Office as the minister responsible for co-ordinating its policies for combating drugs and organised crime.

Only since leaving office last year has he been able to say what he really thinks of the "disastrous" drugs policies pursued by successive governments.

He would decriminalise the possession of drugs which are currently banned and establish a legal framework to regulate their distribution and supply.

"Doctors should do the prescribing. Not the pushers in dark alleys or next to the schools," he told me during a wide-ranging interview in our BBC Westminster studio.

The present policies, he believes, are counter-productive. "You can break up the crime syndicates, but the drugs will still get through and provide massive fortunes for criminal empires and even undermine government itself in some countries."

I suggested to him that any UK government advancing such policies would face a welter of accusations that it was going soft on drugs.

That drew him into a intriguing reflection: "In power I was allowed to move our drugs policy a little bit, but I couldn't get consensus to move it any further.

"On the back benches you can have your say, but no power to do anything."

High speed rail

Our conversation goes to the heart of that perennial political dilemma: how do you balance an individual's conscience with the need to secure sufficient collective agreement to get the job done?

And drugs policy is not the only area where the newly liberated Mr Ainsworth is enjoying saying it as he sees it.

He has equally strong views on plans for a network of high-speed rail services and for a new generation of directly elected mayors in 20 major cities including Coventry.

Would he be interested in running for the job himself?

To find out the answer to these, and other challenging questions, I hope you will join me for this week's Politics Show from 12.00 on BBC One on Sunday 20 November 2011.

Don't forget that you can follow me on Twitter @PatrickBurnsBBC