Baron Hague, better known to most of us as William Hague, hasn't given a TV interview on politics since he retired at the election.

Today this former foreign secretary and ex-Tory leader talks to me and weighs into perhaps the most important political battle of this parliament, whether we should leave the EU.

What is striking is that someone who for many years was regarded as on the sceptical wing of his party, and who insists he remains a critic of much of how the EU operates, is warning that to leave the EU now could have devastating consequences.

He fears it would undermine the stability of Europe when it is facing "great economic and security challenges" and could lead to the "disintegration" of the UK - by precipitating the secession of Scotland.

Hague makes it clear that he would like to vote on the same side as the prime minister in the referendum. So is there any chance of David Cameron recommending the UK should leave the EU?

Hague thinks that's unlikely:

Nor does this former foreign secretary believe it would be a reason to vote for withdrawal if the prime minister fails to persuade the rest of the EU to allow him to implement his election manifesto pledge - to restrict welfare and tax-credit payments to migrants only after they have been in the UK for four years.

Hague says there are other ways to skin this cat:

On a different tack, Hague was perhaps surprisingly frank that he did not expect the prime minister to announce during the last election campaign that he would resign by 2020. He says honesty from the prime minister on his desire for a new life was probably the best policy, but...

So given that it is widely believed the Mayor of London Boris Johnson is gagging to succeed David Cameron as prime minister, doesn't it complicate Johnson's decision on whether to back Cameron in the referendum that if Cameron loses there may be a vacancy at Number 10 earlier rather than later?

And why on earth has Hague retired from the government at an age when some ministers are only just getting going?