AS Chancellor, Gordon Brown was adept at wrong-footing the Opposition with a surprise or two at Budget time, and he's relishing every opportunity to undermine the Tory Party as Prime Minister.

His decision to invite Baroness Thatcher in through the front door of 10 Downing Street yesterday is surely much more about sticking the knife into David Cameron than demonstrating his respect for his illustrious predecessor.

Photographs of Lady Thatcher shaking hands with Mr Brown outside Number 10 were, in our view, deliberately timed to draw attention away from the launch of the Tories' much-vaunted "green revolution".

Paul Kenny, general secretary of the GMB, argues that it was a huge mistake for a Labour leader to invite Lady Thatcher back to her former home.

But Mr Brown knows the propaganda value of those pictures, just as he knows that his invitation to Tory figures to join his "Government of all talents" in specific areas of expertise carries the bonus of destabilising the Tories.

And what may be even more damaging to Mr Cameron is that Lady Thatcher was happy to go along with the ruse.

Given a choice of dates for her visit, she chose not to avoid what was sure to be a big day for the Tory leader.

An oversight by an 81-year-old woman in failing health, or a deliberate move by someone who sharply disapproves of the current direction of the party she served with such distinction?

We suspect it is the latter.