The SS United States still waits to be restored in Philadelphia after being withdrawn from transatlantic service in 1969

The latest P&O "superliner" Britannia has been officially named by the Queen but what happens after cruise liners are past their sell-by date?

In their heyday ocean liners were the most advanced and luxurious forms of transport. The largest moving objects ever created by humans, they elegantly carried everyone from immigrants to politicians and film stars.

But like all good things, their lifespan must come to and end. For many, the future is bleak - the scrap yard and the possibility of ending up as razor blades beckons.

A select few, though, have escaped the scrap yard's blow torch.

The rusting hulk

Image copyright SS United States Conservancy Image caption Rust in peace: The SS United States has spent more years laid up than she did in service

SS United States - flagship of the United States Line - won the Blue Riband for the fastest transatlantic crossing on her maiden voyage in 1952 - a record the ship holds to this day.

However, like her rival Cunard ships - the Queen Mary and Queen Elizabeth - she could not compete with the fast and cheap commercial jet aircraft that soared overhead. After just 17 years at sea, she was withdrawn from service in 1969.

Sold in 1978, she went through a succession of owners and is now a gently rusting hulk, moored at a pier in Philadelphia, her former glories almost forgotten.

But there is hope the ship's future could still be bright. As of 2010 the ship has been owned by the non-profit SS United States Conservancy, which aims to restore her and convert her into a museum and retail/office development.

Susan Gibbs, its executive director, is the granddaughter of William Francis Gibbs, the naval architect who designed the ship.

"Despite the peeling paint and forlorn appearance, the ship is structurally very sound," she said.

Image copyright SS United States Conservancy Image caption In her heyday the SS United States was the most technologically advanced ocean liner afloat

The hotel

Image copyright Getty Images Image caption The Queen Mary and her sister ship the Queen Elizabeth provided a twice weekly transatlantic service for Cunard between the 1940s and 1960s

One of the world's most famous transatlantic liners, the RMS Queen Mary had a glittering career. She won the Blue Riband, counted Elizabeth Taylor, Bob Hope and Winston Churchill among her passengers and carried thousands of troops across the globe during World War Two.

Some 200,000 spectators gathered at the John Brown Shipyard in Clydebank for the christening of "Hull 534", when the Queen Mary was launched in 1934. As well as the largest and fastest liner of her time, she was the last word in ocean-going luxury and Art Deco interior design.

But times changed. In 1967, after 1,001 Atlantic crossings in 31 years, she was retired by operators Cunard. That was not the end of the line for the "grand old lady" of the seas though.

The City of Long Beach, California, purchased the ship and converted her into a floating hotel and maritime museum in 1967.

Image copyright Cunard Image caption The Queen Mary was sold to the City of Long Beach, California for $3,450,000 in 1967, and is pictured here with Cunard's RMS Queen Mary 2

The liner remains a popular attraction, a long way from the cold waters of the North Atlantic and even further from her beginnings at the John Brown Shipyard.

In retirement she has provided the backdrop for many film and TV productions, including Assault on a Queen and Poseidon Adventure.

The multi-purpose attraction

Image copyright Getty Images Image caption The SS Rotterdam was the flagship of the Holland America Line and became known as "La Grande Dame" during her seagoing years

The sleek design of the grey painted SS Rotterdam was ultra-modern when she entered service in 1959 and would go on to inspire the generation of cruise ships that followed.

In the 1990s, under the ownership of Premier Cruises, the ship was renamed The Rembrandt. Her future looked bleak when Premier Cruises went bankrupt in 2000, however.

After a long period of inactivity in the Bahamas, the Rembrandt escaped scrapping - the fate of so many of her generation of liners - when the City of Rotterdam granted the ship a permanent berth.

Returning to her original name and undergoing an extensive restoration, she eased back into her old home port in 2010 to a heroine's welcome and began a new life as a museum, hotel, and training centre.

Image copyright Getty Images Image caption The SS Rotterdam was built in the city from which she took her name, and is now permanently moored there as a hotel, visitor attraction and college

The liner in limbo

Image copyright Getty Images Image caption The QE2 replaced the Queen Mary and Queen Elizabeth in 1968 and went on to serve as a troop-carrying ship in the Falklands War

The beloved flagship of British merchant shipping, the Clyde-built Queen Elizabeth II was retired in 2008 after almost 40 years.

Sold with the promise of a peaceful retirement after conversion into a luxury hotel in Dubai, the project appears still not to have begun seven years later.

The QE2 replaced the Queen Mary and Queen Elizabeth on the North Atlantic route in 1969.

The 293.5m (963ft) long Cunard flagship carried almost 2.5m passengers and completed more than 800 Atlantic crossings.

She retired in 2008 and was sold for £50m to the United Arab Emirates real estate developer Nakheel, leaving Southampton for the last time on 11 November 2008.

Image copyright QE2 LONDON Image caption Plans have been produced to moor the QE2 on the Thames in London

Plans have stalled and a variety of alternative proposals have been floated, including mooring the ship permanently on the River Thames in London, where she would become a hotel and the capital's "new landmark".

John Chillingworth, managing director of London QE2, is confident the London plan is the most viable option for the liner. He explained that work is ongoing to get the ship back to the UK, as a 500-room floating hotel and entertainment venue that would provide a working example of "the last great British-built liner".

"QE2 is unique and has a fantastic heritage that is linked to many British people and their families," he said.

For the time being at least the QE2 languishes in obscurity in Dubai awaiting her fate. But as others have proved - there might still be life in the old liner yet.

Image copyright Getty Images Image caption Sailing into an uncertain future - the QE2 visited Australian waters for the last time in 2008 before being retired to become a floating hotel in Dubai

The Great Liners

RMS Queen Mary, Cunard Line

81,237 gross tonnes

Built at John Brown Shipyard in Clydebank

Launched on 26 September 1934

Speed of 28.5 knots

SS Rotterdam, Holland America Line

39,674 gross tonnes

Built at the Rotterdam Drydock Company mij

Launched 14 September 1958

Speed of 21 knots

SS United States, United States Line

53,329 gross tonnes

Built at the Newport News Shipbuilding, Virginia

Launched in 1951

Speed of 38.32 knots (top speed)

Queen Elizabeth 2, Cunard Line