The move drew a mixed reaction from Jordanians, confused by the speed of the decision days after King Hussein returned from six months of cancer treatment in the US.
"I'm shocked. I can't believe that he has got rid of Crown Prince Hassan so brutally," one royal-watcher said. "The prince has been waiting in the wings for the last 35 years."
Prince Hassan's reaction is unknown, but palace sources are discounting reports from Egypt that he has moved his personal fortune abroad in preparation for an early departure.
The royal palace failed to make an official announcement of the changes. Insiders say King Hussein sent two envoys to Crown Prince Hassan last Friday to tell him he was no longer in line for the throne.
After a family meeting on Sunday, the King confirmed Prince Abdallah's return to a position he held once before, from 1963 to 1965, as an infant.
King Hussein appointed his brother to the post in 1965 because of a series of assassination attempts and amid concerns that a long regency would destabilise the country.
The poor performance of Crown Prince Hassan during the King's long absence was the real reason behind his sacking. "The King felt he was too interfering. He tried to influence what the government was doing too much," said one courtier.
King Hussein returned from the Mayo Clinic, Minnesota, to a tumultuous reception in Jordan last week, promising "sweeping reforms".
While Jordanians have a form of democracy, including elections, government by cabinet and ministers, real power remains with the royal family.
Suggestions that American and British officials have tried to influence the King to move in a more democratic direction have been dismissed by the palace as "nonsense".
Speculation that 18-year-old Prince Hamzah, the eldest son of King Hussein's marriage to American-born Queen Noor, would be made crown prince was wide of the mark, although the monarch has made it clear that Prince Hamzah should take over the throne in the event of Prince Abdallah falling ill or abdicating.
Prince Abdallah is considered an energetic soldier and attained the rank of major-general in the army last year. He is also known to be interested in economics and development issues and is married to Rania al-Yassin, a Jordanian of Palestinian origin.
In a country where by some estimates more than 65 per cent of the population is Palestinian, the marriage was considered a shrewd gesture.
Jordanians refused to answer questions on the streets yesterday about whether they were happy with the new crown prince's half-British ancestry. "The King has chosen him and I think that is enough" said one man waiting at the taxi rank.
His mother, English-born Toni Gardiner, known in Jordan as Princess Mona, has continued to live in the country since her 1972 divorce from the King.Reuse content