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History of the Atlantic Cable & Undersea Communications
from the first submarine cable of 1850 to the worldwide fiber optic network

Cableships Iris (3) and Monarch (5)
by Bill Glover

CS IRIS (3) and CS MONARCH (5)

CS Monarch (5) crest.JPG (27720 bytes) Keel laid 1973 by Robb Caledon Shipbuilders Ltd.

Sister ships, built to the same design. Commissioned: CS Monarch 1975, CS Iris 1976.

Length 97.245m. Breadth 15.029m. Depth 5.5m Gross tonnage 3873

Both ships were built for the Post Office Corporation (formerly the GPO) for cable repair work around the British Isles and as far as Cape St Vincent, the Atlantic continental shelf and the Skaggerak and were based at Southampton.

In 1982 CS Iris saw active service in the Falklands during the war with Argentina (see below).

The ships were transferred to BT International in 1983, when the POC telecommunications service was privatised. Later the name was changed to BT (Marine) Ltd. In 1994 both ships were sold to Midland Montague Leasing and chartered to Cable & Wireless (Marine) Ltd. When the Cable & Wireless fleet was sold to Global Marine Systems Ltd in 1999 the charter was taken over and their base was moved to Portland Harbour, Dorset.

CS Monarch (5) as launched (1975)

CS Iris (3) as launched (1976)

Ship photos below copyright © 2006 T. F. Watson, UK
CS Monarch 5 Stern.jpg (46559 bytes) CS MONARCH (5).jpg (60820 bytes)
CS Monarch (5) at the Global Marine Ltd. depot, Portland Harbour, Dorset, UK


After being fitted with a larger helicopter deck, CS Iris left Devonport for Ascension to transport stores from there to the Falkland Islands. During seven months of active service CS Iris steamed over 45,000 miles and was involved in over 800 helicopter operations in a period of 74 days.

CS Iris (3) arriving back at Southampton on the 30th November 1982

A short film on this voyage, “CS Iris to the Falklands and Back”, was released in 1983. The film was produced on videotape by the British Telecom photographic unit and narrated by Jim Hodgson, managing director of BT International at the time. It can be viewed on line at the BT Archives

Commemorative plaque for CS Iris (3)
Hand Painted by Dextercrest Ltd, London
Plaque courtesy of Keith Lafferty

Cableships Index Page

Last revised: 27 May, 2023

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