In the early part of his life he had been at sea in the Merchant Navy. During the war he was wounded, and while recuperating he read voraciously and began to write. He became a respected author and story-teller. His work was published in both local and national magazines, and what is probably his best known work, 'The Night that Mouat was Lost', a short story about The Tragedy at Spiggie 1887 appeared in the New Shetlander and eventually in the anthology 'Nordern Lichts'.
His family were partners in the business of R & T Henderson of Whillygarth, Scousburgh, and Tom inherited croft land, which included Spiggie Loch, the island of Colsay, and the small 'Henderson's Hotel' (now Spiggie Lodge), which he operated for a number of years in partnership with his wife.
He was co-opted on to the Zetland County Council (ZCC) in 1952 to fill the vacancy created by the departure of R. H. W. Bruce, a seat he held for the next 11 years. The final three, from 1960-63, were also as Convener of the County.
He served at one time or another on numerous public committees, including the Board of Management of Shetland Hospitals, Lerwick Harbour Trust (now Lerwick Port Authority), the Fishermen's Mission (R.N.M.D.S.F), and the Shetland Folk Society. He was also a founder member of both the Shetland Group and the Shetland Movement.
Around 1970 he sold most of his property at Scousburgh, only retaining Colsay, and purchased the The Old Manse at 9 Commercial Street, Lerwick, which, dating from the late 1600s, is generally believed to be the oldest inhabited house in Lerwick.
In 1977 he was made a Fellow of the Society of Antiquaries of Scotland, and was awarded the M.B.E.
As curator he wrote the introduction and captions to the book Shetland From Old Photographs. Henderson was an internationally respected expert on Shetland's maritime history, and in the 1940s planned a work on Shetland shipwrecks with R. Stuart Bruce, never completed. His essay 'Shipwreck and underwater archaeology in Shetland' appears in B Smith ed., Shetland Archaeology (1985).