It was the worst of omens for the gleaming new ship embarking on its maiden voyage.

As the Titanic left Southampton docks for a journey that has gone down in history, the ship came close to hitting two other liners.

Had they collided, it would have cut short the Titanic's ill-fated voyage to New York and may well have averted the catastrophe that was to claim 1,500 lives when the boat struck an iceberg on April 14 1912.

The near miss is described in a letter from the Titanic's chief engineer Joseph Bell to his son Frank, which is to go under the hammer later this month in Devizes, Wiltshire.

Mr Bell told his son, who was training in Belfast to be a ship's engineer like his father, how the mooring ropes of the New York and Oceanic liners broke as the Titanic passed, causing the New York to set off across the river.

''I hope you got to Belfast alright to start work on time, I got your wire from Liverpool, we have made a good run from Southampton, everything is working A1,'' Mr Bell wrote.

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''We nearly had a collision with the New York & Oceanic when leaving Southampton, the wash of our propellers made the two ships range about when we were passing them, this made their mooring ropes break and the New York set off across the river until the tugs got hold of her again, no damage was done but it looked like trouble at the time, keep well and be a good lad, regards to Mrs Johnston.''

Mr Bell, who died in the disaster leaving behind wife Maud and four children, had transferred to the Titanic from the Olympic and oversaw its construction in Belfast.

Andrew Aldridge, from Henry Aldridge and Son Auctioneers, said: ''It's a bit of a sliding doors moment, which describes a near miss that would have changed history.

''If the Titanic had collided with the New York or Oceanic as she left Southampton, the ship would have been delayed and may well have not have come into contact with an Iceberg ''He also ironically describes everything as 'working A1' on board the liner when she left Southampton.''

Mr Bell's letter is estimated to fetch between £10,000 and £15,000 when it goes under the hammer on October 18.