HE became a national hero when his ship rescued hundreds of survivors from the stricken liner Titanic.

Now the sextant used by Sir Arthur Rostron to set a course to the site of the disaster is set to go under the hammer. The device, owned by the family of the famous captain of RMS Carpathia, is expected to fetch £70,000 once bidding comes to an end at Henry Aldridge & Son, a leading auctioneer of Titanic memorabilia.

Sir Arthur lived in Chalk Hill, West End, and was buried after his death in 1940 at the West End Road graveyard.

His prompt response to the sinking of Titanic in April 1912 is widely credited with saving more than 700 lives.

Sextants were used to measure the angle between a celestial object and the horizon and were an essential part of navigation at sea at the time. The polished brass instrument up for sale this weekend was acquired by Arthur Rostron whilst serving as a cadet at the Merchant Navy Cadet School H.M.S. Conway in 1883 and was used throughout his career. His Great Granddaughter Janet Rostron said: "The Sextant has never been on public display before and has been kept within the Rostron family, passed down from father to son for the last 100 years.

"The Sextant would have been used by him throughout his career and would certainly have been the instrument he used to navigate through the ice flows. "Once Sir Arthur retired the sextant was passed onto his son Harry and then onto my father.”

Sir Arthur was described by his Grandson David as “a quiet, kind and dignified man." The device is being billed as a “once in a lifetime opportunity” for a museum of collector.

Andrew Aldridge, from the Wiltshire-based auction house, called it “a very important piece belonging to a very important man.”

“Sir Rostron received the message Titanic was sinking but he was actually heading towards England at the time. “This is the sextant Sir Rostrant used to reset his ship's course and he was responsible for rescuing the few that were saved. Without the sextant he certainly would not have been able to find the last known location of the Titanic to save lives. It is for that reason this item is very important and very emotive.” Also up for sale is Sir Arthur's bronze Dieges and Clust Carpathia medal, which has been kept in the family since 1912 and is described by auctioneers as “without doubt the finest ad rarest bronze Carpathia medal in existence today”.

The auction takes place on November 24.