LONDON — The Union flag was flying across Whitehall, the center of British government, yesterday in a display of national solidarity against terrorism. Prime Minister Brown has ordered that all government buildings should fly the flag as a patriotic gesture to help create a new sense of Britishness.

No. 10 Downing Street, the Treasury, Revenue and Customs, and the Departments of Culture and Health were among those that had hoisted the flag by yesterday. An official “direction” has gone out that all government buildings that have flag poles should fly the flag 365 days a year.

A spokesman for the Culture Department said Mr. Brown would like other public buildings, such as police stations, prisons, and hospitals, to follow suit. According to a blueprint for constitutional reform published by the Justice Department, symbols such as flags could help to embody a national culture and citizenship. “The Union flag is one of the most recognizable symbols of the U.K. But while in other countries, such as France and the United States, the national flag is regarded as a source of pride, in recent years, the Union flag has all too often become the preserve of political extremists, a symbol of discord rather than harmony,” the department said.

“It is critical that this symbol is not hijacked by those who seek to work against values of tolerance and respect.”