Mr Thomas Threlfall was born in Liverpool, Lancashire, England on 19 October 1867. He was baptised at the church of St Peter, Liverpool on 10 November 1867 and at the time his family were living on Hornby Street, Liverpool.

He was the son of James Threlfall (b. 1844), a carter, and Grace Wharton (b. 1843), Liverpool natives who had married in 1866.

He had five siblings, all sisters: Margaret (b. 1869), Emily Jane (b. 1870), Catherine Mary (b. 1878), Isabella (b. 1874) and Mary Ellen (b. 1880).
He first appears on the 1871 census living with his family at an illegible address in Liverpool; by the time of the 1881 census the family were living at 70 Portland Street in the same city and Thomas was still a schoolboy.

In June 1901 Threlfall was working as a trimmer aboard Tauric, his address at the time being 68 China Street, Liverpool. By February 1903 he was a fireman aboard Cedric and gave his address as 85 Ellison Street. During 1906 he was working as a greaser aboard Empress of Britain, prior to which he had served aboard Baltic; during this time he gave his address as Ashfield Street. The following year he was working as a leading fireman aboard Majestic, still at his Ashfield Street address.

On 17 May 1892 he married Margaret Downes (b. 31 May 1870), also of Liverpool, the daughter of Simon Downes and Margaret Meara. Their first child, Margaret, was born on 22 June 1894 and the small family appear on the 1901 census living at 68 China Street, Everton, Liverpool and Thomas was described as a dock labourer. Another daughter, Norah, was born in 1909.

By the time of the 1911 census Thomas was absent and presumably at sea; his wife and daughters were recorded as living at 128 St. Martin's Cottages, Liverpool, the home of his mother-in-law Margaret Downes.

On 6 April 1912, when Threlfall signed on for the maiden voyage of Titanic, he gave his address as 128 St. Martin's Cottages, Liverpool. His previous ship had been Olympic and as a leading fireman he could expect monthly wages of £6, 10s.

Threlfall reported that after the collision his stokehold, number 4, was dry and the fires were burning as usual. The watertight doors had been closed but were reopened to bring through an engineer with a broken leg (Jonathan Shepherd) before being closed again.

Threlfall was rescued in boat 14.

In 1913 it was reported that he was responsible for the Liverpool branch of the British Seafarer's Union. During WWI he continued to serve in the Merchant service and was aboard SS Arcadian when that ship was transporting wounded from Salonika in Greece to Alexandria in Egypt. On 15 April 1917, two years to the day of the Titanic disaster, Arcadian was torpedoed by a German U-boat and sank in just over five minutes; Threlfall again escaped with his life and later stated:

"It was the same day of the week, and the same date of the month that the Titanic went down ... and I have come safely out of both affairs..."

Challenged to what was the worse of the two experiences he stated:

"Well, the Titanic stopped afloat for a couple of hours and we had time to turn around, but of course you could not live in the water that night. This time we had calm sea and warm weather, and you had a chance, but with the Titanic you died in the water almost as soon as you got in."

Thomas became a widow when his wife died in 1929; he himself died in Liverpool on 10 January 1934.   He is buried in Kirkdale Cemetery, Liverpool, England (Section 21, plot 140) in an unmarked public grave.

His daughter Margaret was married in 1917, becoming Mrs Joseph Shirley, and she had five children. What became of her is unclear but she possibly died around 1970. The fate of Thomas' daughter Norah is also uncertain.