By Nick Assinder
Political Correspondent, BBC News website
Tony Blair already has a list of contentious policies on his pre-retirement agenda, yet he has now added one of the most controversial going - a possible revival of nuclear power.
As the Greenpeace demonstration so dramatically showed, if the prime minister opts to go down this route to bridging the energy gap, as many expect, he will have a serious fight on his hands.
Energy review will look at new nuclear stations
And it will not just be Greenpeace and other environmental groups who will lead the opposition to any proposal to start building new nuclear power stations.
There are plenty of Labour backbenchers, led by former environment minister Michael Meacher, the Liberal Democrats and a significant number of ministers deeply opposed to any return to a nuclear energy programme.
Indeed, the whole issue was once a core part of Labour policy.
Current Environment Secretary Margaret Beckett is remembered as an old opponent although she insists she has an open mind on the issue, albeit with major reservations over cost and waste disposal.
Health Secretary Patricia Hewitt and Northern Ireland Secretary Peter Hain are also believed to be opposed or at least have serious doubts.
On the prime minister's side, however, are Chancellor Gordon Brown - as long as he doesn't have to pay for any of it - Trade Secretary Alan Johnson and Defence Secretary John Reid.
But this is early days and, while it is believed the majority of the cabinet are prepared to back a return to nuclear, it would be rash to be too positive about how individual ministers might finally vote.
Blair has prepared the ground for change
Yet the prime minister is said to believe this is the only way to fill the looming energy gap and he has been preparing the ground for a debate on the issue for many months.
The election manifesto included the pledge to review the role of nuclear, the prime minister highlighted it in his party conference speech in October and has returned to the subject on a number of occasions since, including at the Commons Liaison committee.
Tuesday was supposed to be the day when he would formally unveil that review and kick off this most heated of debates.
Well he got the second bit before he even managed to deliver his speech and as he said himself when he finally got to speak: "It is a difficult and challenging issue, but that is like most tough issues."
It certainly is. And the demonstration is probably only the start.