As he looked forward over the past decade to the day he would at last enter 10 Downing Street, Gordon Brown would not — even in his wildest dreams or nightmares — have imagined that within a few months he would be nationalising a bank.

Nationalisation has been a word conspicuously missing from the new Labour lexicon, evoking memories as it does of the days when Labour's machine was in the grip of the Left, pursuing policies that were eventually to make it unelectable.

So when Mr Brown and Alistair Darling were being asked why they did not go for this option much earlier, their questioners knew the answer. Although they accepted that public ownership was always an option, it was an alternative that they were prepared to grasp only as a very last resort.

Mr Brown and Mr Darling did not want to do what they have just done, but in the end they decided it was their only choice.

When they stood side by side in the state dining room at No 10 today, Mr Brown and Mr Darling were not apologising for their actions and Mr Brown, in particular, was utterly defiant about them.

In fact, events had forced their hand. They had taken the only course open to them, and now they lined up to defend nationalisation (they said it was only temporary on countless occasions) on the ground that it was in the public interest.

“We will and always have put the interests of taxpayers first,” Mr Brown said. “We will not retreat from taking the tough long-term decisions that are necessary.”

The “soft” option, insisted the Prime Minister, would have been to go for one of the private deals on offer until 2pm yesterday. But neither of them would have produced the return for the taxpayer that was necessary given the level of subsidy they were requiring.

Time and again in the face of tough questioning Mr Brown said that the Northern Rock decision showed that the Government was ready to take the right long-term decisions. And it was “entirely possible” that in the end the taxpayer would make a profit when adverse market conditions improved.

Mr Brown also defended his successor's record at the Treasury, despite a series of high-profile controversies over tax changes as well as the Northern Rock problem.

“We are dealing with a global financial situation; I believe we have been better prepared — because of the actions of Alistair Darling in the Treasury — than in other countries,” he said.

The “test of economic competence” was the UK's stable economy and higher growth and employment than competitor nations, he added.

Mr Brown insisted that the problems in the US sub-prime mortgage market, which led to the collapse of Northern Rock, could not have been foreseen. “We are dealing with a global financial turbulence that is affecting every country, but particularly the main industrialised continents,” he said.

Mr Darling said that the loans made to Northern Rock by the Bank of England were secured against the bank's assets, and that there had been no call on any of the guarantees issued by the bank. “They have been given but they have not been called, therefore there has been no cost,” he said.

“We remain confident therefore that the Bank of England will be able to get its money back.”

Mr Brown had to duck the inevitable question about whether Northern Rock would still be in public ownership at the time of the next election. That, of course, depends on when he decides to call the election and what happens to the markets between now and then.

If Mr Brown felt regret about what has happened he was not showing it. The nationalisation decision was “the right move, at the right time, for the right reasons”.

Times Recommends

• Iran arrests relatives of opposition leaders
• Banksy rival has final word in art feud
• Electrician travels 175 miles to change bulb