Before October 1876 mails were conveyed between Southampton and Cape Town every alternate week in terms of a contract concluded between Her Majesty's Postmaster General and the Union Steam Ship Company Ltd.
On 5 October 1876 two new contracts commenced that ensured a weekly mail service between Great Britain and the Cape Of Good Hope. One contract was concluded between the Crown Agents for the Colonies and the Union Steam Ship Company Ltd and the other between the Honourable John Charles Molteno, Colonial Secretary of the Cape of Good Hope, and the Castle Packets Company. In terms of these two contracts a vessel of the Union Steam Ship Company commenced the north bound voyage from Table Bay to Plymouth and Southampton on Tuesday, 3 October 1876 and a vessel of the Castle Packets Company to Table Bay on Friday, 6 October 1876. Both journeys had to be completed in 27 days. The two mentioned shipping companies amalgamated in 1900 under the style of the Union-Castle Mail Steamship Company Ltd.
Because the company provides a fast and reliable service between Cape Town and Southampton, its ships have ever since been used without interruption on a contract basis for the transportation of sea mail from Cape Town to the United Kingdom and the continents of Europe.

(from an insert printed by Aurora Printers.)

The Island of St Helena has a beautiful set of Mailship stamps which I only discovered recently. The set of 4 stamps feature the Walmer, Llangibby, Stirling and Pendennis Castles.

The Final Sailing of the Mailships

Pendennis Castle. 01 June 1976	Windsor Castle. 6 September 1977
SA Oranje. 03 October 1975	SA Vaal. 27 September 1977

The Ship Society of South Africa released a series of 4 special envelopes to commemorate the final departure of the last 4 mailships. Ironically the envelope which featured the Windsor Castle also bore the Ocean Service Mail Contract stamp as featured above. Barely a year after the centenary of this contract, one of the last of the Union Castle mailships was sailing from our shores.

The Safmarine Mailships

SA ORANJE

SA VAAL

The Union Castle Mailships Pretoria Castle and Transvaal Castle, were transferred to Safmarine in 1966 and renamed SA Oranje and SA Vaal respectively. They were re-registered in Cape Town and both were used on the mail run until the Oranje was withdrawn and sold for scrapping in Kaohsuing in the mid 1970's. The Vaal was in service till 1977 when she too was withdrawn and sold to the fledgling Carnival Cruise Lines. As Carnival moved towards megaships she too was sold, this time to Dolphin Cruise Line for who she operated as IslandBreeze until Premier Cruises acquired her along with Dolphin Cruise Lines. When Premier folded she was laid up at Freeport in the Bahamas and in April 2003 it seemed as if the end was near and she commenced her final voyage to the breakers in May. She was finally beached at Alang on July 13th 2003.

On 5 December 2007, the South African Post Office issued a series of 5 stamps, based on the paintings done by Peter Bilas which were used in the book "Mailships of the Union-Castle Line" by CJ Harris and Brian D Ingpen. commemorative cover, featuring the Scott is also available.

Arundel Castle	Edinburgh Castle
SA Vaal	Kildonan Castle
Dane	The Scott

RMS Dunnottar Castle

The Dunottar Castle is one of the older ships still afloat and has spent most of her life as a cruise ship. She was built by Harland & Wolff, Belfast, and launched on 25 January 1936. She was primarily used on the London (Tilbury) - round Africa service until the outbreak of WW2, when she was converted to an armed merchant cruiser, and later to a troop transport. In 1949 she resumed her London - round Africa service. In 1958 she was sold to Incres SS Co, who renamed her Victoria and substantially rebuilt her in Rotterdam. She entered service in 1960 on New York-West Indies cruises.
In 1964 she changed hands once again, this time to Victoria SS Co, a subsidiary of Swedish company Clipper A/B, she retained her name, and Incres Line as agents. Chandris Cruises bought her in 1964, and she resumed sailings as The Victoria in June of 1976. She cruised in Europe and the Caribbean until 1993, when she was sold to Louis Cruise Lines and renamed Princessa Victoria for use on cruises from Cyprus. In 2002 it was reported that she was to be taken up for service as a hotel ship in London, this sadly never came to pass and the Princessa was laid up and in 2004 sold for scrap. She arrived at the breakers at Alang on 25 May 2004.

RMS Southampton Castle

The Southampton Castle has the distinction of being the last mailship to make the run for the Ocean Service Mail Contract. Her last northbound voyage commencing on 11 October 1977. Her sister ship, Good Hope Castle was involved in a serious fire near Ascencion Island in 1973, the 2 stamps above may actually refer to the Good Hope as opposed to the Southampton as stated. The 2 sisters were 180m long with GRT of 10538 tons. Service speed was 22,5 knots and they were designed to complete the mail run in 11,5 days. The sisters were both sold to Costa Crociere in 1978, Good Hope being renamed Paolo C and Southampton Castle renamed Franca C, Both were scrapped in 1984.

Brian Bunyard has informed me that the following stamps also feature Union-Castle themes.
An issue from South West Africa from around about the mid to late thirties was a transport stamp depicting a train an aeroplane and a ship which could be either the Athlone / Stirling or Capetown Castle.
In 1969 St Helena issued a series of four stamps depicting " Brig Perseverance", R.M.S Dane, "S.S.Llandovery Castle", and the R.M.S Good Hope Castle.
In 1980 a series of four stamps issued from Ascension Island called History Of Mail Transport depicts Garth Castle on the 15P
If anybody does have a copy of these.....