Britain's heir-to-the-throne Prince Charles and Prince William took centre stage at the opening of parliament on Tuesday, replacing the 96-year-old Queen Elizabeth who missed the grand set-piece event for the first time in almost six decades.

With the queen forced to withdraw on Monday due to a recurrence of mobility issues, 73-year-old Charles arrived at the Palace of Westminster to read out the government's legislative agenda.

Charles, who had attended the opening of parliament alongside his mother in recent years, started reading out each bill by saying: “Her majesty's government will...".

The State Opening of Parliament is an event of huge pomp and pageantry which traditionally sees the queen travelling to the assembly in a State Coach, escorted by mounted soldiers in ceremonial uniform, while the Imperial State Crown and other regalia travel ahead in a carriage of their own.

The monarch dons the Robe of State before leading a procession to the House of Lords upper chamber where she sits on a throne and formally opens a new session of parliament, reading a speech written by the government outlining its legislative plans.

The queen has missed the occasion only twice during her 70-year reign — in 1959, and 1963, when she was pregnant with sons Andrew and Edward.

The queen, who has missed a number of public engagements since she was hospitalised for a night last October for an unspecified illness, had to issue a 'Letters Patent' to authorise Charles and William to carry out her role at the constitutional event.