A three-quarter-length portrait slightly to right in a black velvet coat with a black silk shoulder knot on his right shoulder and sleeves opening from shoulder to cuff. His sword hangs from a heavily embroidered gold baldric that he holds with his right hand. He wears his own black hair and a moustache. There are russet curtains in the left background and a ship in action on the right.

Apart from some service in the Mediterranean in 1660 little is known of him until, under Sandwich, he fought as Rear-Admiral of the Blue squadron off Lowestoft in 1665. He was knighted for this service. Shortly afterwards, still under Sandwich, he went to Bergen to attack Dutch Indiamen but was beaten off, since the Dutch were assisted by the Danish shore batteries. Despite this defeat he was successful the following year as a flag officer at the Four Days Fight and the St James's Day victory.

The portrait is inscribed 'Sir Thomas Tiddyman' and is one of the 'flagmen' portraits commissioned by Charles II's brother James, Duke of York after the Battle of Lowestoft. This was the first major action of the Second Dutch War, in which James commanded the fleet. It was seen in Lely's studio by Pepys and mentioned in his diary for 18 April 1666 as one of the portraits then either begun or finished.

Lely, a Dutchman who arrived in England in 1641 after the death of Van Dyck, soon became his successor as leading portraitist of the day. He worked for Charles I, continued to flourish under the Commonwealth and Protectorate, and after the Restoration of 1660 was appointed Principal Painter to Charles II. The full 'flagmen' set consists of thirteen individual portraits, of which George IV presented eleven plus a copy of that of Admiral Sir John Lawson (BHC2833) to Greenwich Hospital in 1824. The originals of Lawson and of Prince Rupert were retained in the Royal Collection, although William IV presented an extended full-length copy of the latter (BHC2990) to the Hospital in 1835.