The Ark Royal will now be put through a series of sea trials

The 20,000-tonne warship arrived at Portsmouth Naval Base on Saturday morning having undergone the two-year upgrade at Rosyth in Scotland.

More than 1,000 people lined the dockside to welcome the Ark Royal back.

The refit enables her to carry the Army Apache attack helicopter along with the RAF Chinook helicopters and the Navy's anti-submarine helicopters.

The vessel has undergone major upgrades of its communication systems and electronic charting.

It has also received a towed sonar decoy system for defence against submarines and has been fitted with a new mast.

A Royal Navy spokesman said: "It is planned that HMS Ark Royal will remain in service until the Royal Navy's new, larger carriers are due to enter service in the next decade."

The Navy plans to replace its whole fleet of aircraft carriers in 2012.