By the BBC's John McIntyre

It is exactly 90 years since the sinking of the mighty Titanic on her maiden voyage from Southampton to New York.

At 11.40 pm on 14 April 1912, the crow's nest bell tolled three times, followed by three words that sealed the ship's fate.

"Iceberg, right ahead!" cried the lookout Frederick Fleet.

She was a true giant, the most lavish ship of a new generation of passenger liners.

Perhaps ironically it was her sister-ship, the Olympic, which sailed first and received all the kudos for her owners, White Star Line.

But all that changed when at 2.18 am, just a few hours after Fleet spotted the iceberg, the Titanic heaved vertically and vanished into the depths of the North Atlantic.

The latest Hollywood film about the Titanic was a global hit

Eyewitness accounts of the survivors formed the basis of the many inquiries that followed.

Titanic had been travelling at just over 20 knots, when the iceberg scraped along her starboard side.

Captain Edward Smith, known as the "millionaire's captain", was initially told there was no significant damage but an inspection of Titanic's watertight compartments revealed she was in fact in grave danger.

Excessive speed

A British inquiry later concluded the disaster was caused by excessive speed.

It was also highly critical of the lack of lifeboats on the ship.

Blame has been laid at the door of many and even today the rows continue.

But it was not until after the oceanographer Dr Robert Ballard discovered the wreck 375 miles southeast of Newfoundland that scientists were able to establish what went so disastrously wrong.

They were able to demonstrate that what appeared to be a relatively harmless tear along adjacent watertight compartments had catastrophic consequences, with the ship unable to cope with the influx of millions of gallons of seawater.

Titanic facts

RMS Titanic was built in Belfast by Harland and Wolff 1,523 people died in the disaster 705 survived and made it to land The largest Titanic memorial is in Godalming, Surrey A menu from the ship raised �25,000 at auction last week

Valuable lessons were learnt which are regarded as vital to today's shipping industry.

Captain Ron Warwick, who is in charge of luxurious modern-day QE2 and who often sails from Southampton to New York, is part of the exclusive club of people who have dived to the wreck.

He is in no doubt about the legacy of Titanic.

"It tells us we can never be complacent, especially as far as technology is concerned.

"Ships are something man creates but one always has to have respect for the sea, rough weather, calm weather, ice conditions, fog and snow."

Benefits from disaster

Capt Warwick said seafarers the world over have benefited from the Titanic disaster.

"It's an unfortunate fact of life that it often takes an accident to improve situations."

An international ice patrol was formed as a direct result of the Titanic tragedy, as well as international laws that require there to be sufficient lifeboats and lifesaving equipment for every passenger.

But could Titanic ever happen again?

The wreck is full of holes and rusting away

"That's not an unreasonable questions," says Capt Warwick.

"It certainly could. To this day we still have some quite serious accidents. As an industry, it's up to us to do our best to ensure it never happens again."

As for Titanic, she is deteriorating rapidly.

Trips to the wreck

Anatoly Sagalevitch is head of the Russian research ship Akademik Keldysh which has been forced to sell trips to the wreck to survive and continue its work.

He has probably visited the Titanic more than any one else.

Over the past ten years, he says, much of the ship has been devoured by rusticles.

"Now all the deck is rusting away and there are big holes in Titanic.

"In four, five maybe six years, the superstructure will collapse. This is not just my view but also of our scientists and engineers."

Perhaps, when it is time to commemorate the 100th anniversary of Titanic, she will be no more.