After four years there, he joined in 1844 the Cunard Steamship Company, Liverpool, owners of the only regular line of steamers sailing between Europe and America, which numbered no more than three the Caledonia, the Arcadia, and the Britannia, all of small tonnage.

At the time the Union Steamship Company, founded in 1853, carried on the principal trade between the United Kingdom and South Africa and had the contract for the mail service.

The enormous improvement of communication between the United Kingdom and South Africa was largely due to Sir Donald and his ships.

In 1875, he was elected chairman of a committee of ship-owners to consider proposed changes in laws affecting the mercantile marine, and he was responsible for important amendments of the Merchant Shipping Act of 1876.

Molteno therefore ordered the South African mail service to be shared equally, between Currie's Castle Company and its older rival, the Union Line.

After lengthy negotiations, Currie agreed to alternating services, speed premiums and other clauses to promote competition.

In 1883, on Currie's representations, the British flag was hoisted at St. Lucia Bay in Zululand, which the Germans would have captured a few days later.

[1] In 1877, Paul Kruger and two others came to the United Kingdom as a deputation from the Transvaal Boers to the British government, begging for self-government.

He remained on intimate social terms with Gladstone, who was on several occasions between 1883 and 1895 his guest with other distinguished persons on one or other of his ships for summer cruises.

New breeds of cattle and sheep were introduced, and large sums expended on the erection and improvement of churches, schools, and cottages.

In 1904 he gave to University College Hospital, London, £80,000 for a school of final medical studies, and £20,000 for a nurses' home and a maternity students' house.

To the University of Edinburgh he gave £25,000 for 'The Donald Currie Lectureship Endowment Fund,' and £6000 for the enlargement of the Students' Union.

[1] He died on 13 April 1909 at the Manor House, Sidmouth, Devonshire, and was buried in the churchyard of Fortingal, beside his Highland home.

In 1880, he was awarded the Fothergill gold medal of the Royal Society of Arts in recognition of 'the improvements which he had introduced into his passenger steamers.'