Lehmann's major painting, The Blessing of the Pontine Marshes by Sixtus V was shown in Paris in 1846 and bought by the French government.

[1] In 1866 Lehmann settled in London, became a British citizen, and painted his best-known portraits.

Amelia's sister Nina married Lehmann's younger brother Frederick, and the extended social circle of the two couples included Charles Dickens, George Eliot, Robert Browning, Lord Leighton, and other prominent figures.

In 1896, a number of his engraved portraits were collected and published as Men and Women of the Century.

He died at his home, Boumemede, Bushey, on 27 October 1905 and was buried in the east side of Highgate Cemetery.