His father died in 1837 and in 1839 his mother married another prime minister, Lord Palmerston, who became Cowper's stepfather.

After entering the Royal Horse Guards in 1830, he was promoted Captain five years later, eventually attaining the rank of brevet Major in 1852.

[1] In 1835, Cowper was elected Liberal Member of Parliament for Hertford, a seat he held for the next thirty-three years, and became private secretary to his uncle Prime Minister Lord Melbourne.

In order to overcome the concerns of Nonconformists that their children might be taught Anglican doctrine, the clause proposed that religious teaching in the new state schools be non-denominational, which in practice meant learning the Bible and a few hymns.

[5] When his mother died in 1869, he inherited a number of estates under his stepfather's will, and so took that year under Royal licence the additional surname of Temple.

The properties included a 10,000-acre estate on Sligo's Mullaghmore peninsula with its unfinished Classiebawn Castle, commissioned by his stepfather, which he completed by 1874.

[6] This was a revival of the junior title held by the Viscounts Palmerston, which had become extinct along with the viscountcy on his stepfather's death in 1865.

He died on 16 October 1888, aged 76, at his home of Broadlands, Hampshire, and was buried at nearby Romsey.