Gordon Brown’s premiership is already being tested by events beyond his control. The terrorist attacks in London and Scotland have occupied much of his time since Friday morning and forced him to postpone until later this week his Commons statement on reviving trust in politics, planned as a centrepiece of his first week in office. For all the carefully prepared attempts to convey an image of change, it will be the sight of the sombre Mr Brown warning the nation to be vigilant that will stick in most voters’ minds.

Premierships are defined by unexpected challenges: the Falklands war and the miners’ strike for Margaret Thatcher; and the 9/11 attacks and Iraq for Tony Blair. Mr Brown has been used to controlling his agenda via the occasional, important announcements that a chancellor has to make. He has rarely done the spontaneous and the immediate. Now, he has no choice.

His appearances so far have been impressive, reinforcing his image as a strong, national leader. But his style is significantly different from that of his predecessor. After the great intuitive actor-manager, we now have the anxious headmaster. Mr Brown is not smooth. There are no memorable phrases. Rather, he is the concerned voice of authority, keen to reassure the public, and not to be hurried, or panicked, into emergency action.

In marked contrast to the desire of Mr Blair and John Reid, the former Home Secretary, to use such incidents to press for draconian powers, Mr Brown has adopted a calmer tone. His immediate aim is national unity and alertness. Questions such as extending the present 30-day detention period and creating new police powers to question suspects after they have been charged should be left until later, and subject to full parliamentary debate.

This lower-key, consensual style chimes with the public mood. It is not the start he planned, or wanted, but it does enable him to dominate the news agenda.

Before the new terrorist threat emerged, Mr Brown’s arrival had gone pretty smoothly. The new Cabinet was sufficiently fresh and younger than the Blair team, to substantiate the claims about change. And while one or two of the outsiders appointed as Lords ministers have raised eyebrows, the inclusion of Admiral Sir Alan West as a security minister and Lord Stevens of Kirkwhelpington, the former Commissioner of the Metropolitan Police, as Mr Brown’s senior adviser on international security issues, have been quickly justified.

No matter that Mr Brown has extended prime ministerial patronage wider than ever. There are now a record 118 ministers and whips in the Commons and Lords, compared with 113 in the outgoing administration and 103 in 1990.

Apart from the meetings of the Government’s emergency committee, Mr Brown has already chaired two full meetings of his Cabinet. In his interviews for the BBC One programme Sunday AM, he referred pointedly to running Cabinet government, not sofa government (for which, of course, Mr Blair was widely criticised).

Mr Brown’s new team of officials and special advisers in Downing Street is strong, and largely imported from the Treasury. But to counter suggestions that a Prime Minister’s department is being created in all but name, Sir Gus O’Donnell, the Cabinet Secretary, has insisted that Jeremy Heywood, the head of domestic policy and strategy, and the two senior foreign policy advisers, work from the Cabinet Office, not No 10. The office politics will rival those of the Yes, Prime Minister series of the 1980s.

So while the public image is all of change, the reality is more familiar — of a renewed, and acute, terrorist threat. There may be a Brown bounce in the polls. But there is no Brown honeymoon. Rather, he is being severely tested from the start. So far, he is standing up well.

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