Seaslug was the Royal Navy's first Guided Missile, and was carried by the County class guided missile destroyers.  The eight ships of this class formed two groups, HM Ships Devonshire, Hampshire, Kent and London were equipped with Seaslug Mk1.  HM Ships Antrim, Glamorgan, Fife and Norfolk were equipped with Seaslug MK2, and later had B turret replaced with four Exocet launchers.  The latter group can be readily identified by the double antennae of their main air-search radar, the type 965.

Seaslug was designed as a shipborne medium-range area-defence surface-to-air missile; the project started in 1949 but it didn't enter service until 1962.  Its task was to destroy medium to high altitude bombers before they could release weapons (including nuclear bombs) aimed at RN warships.  It was subsonic but surprisingly accurate; some sources credit Seaslug with a single-shot kill probability (SSKP) of 92%!  The use of four solid-fuel boost motors in a wrap-around configuration attached to the front half of the missile gave it a good acceleration and obviated the need for large stabilising fins (as were needed for the land-based missiles Thunderbird and Bloodhound).  Guidance was by beam-riding with an active radio fuze, and it carried a large blast warhead. 

Even as Seaslug was entering service, an upgraded model was being planned.  Codenamed Blue Slug this was a faster, longer-ranged version that could carry a nuclear warhead.  The idea of using such a warhead was effectively prevented by the atmospheric test-ban treaty.  All the other improvements, however, were utilised for Seaslug Mk2.  These included longer range, better (infra-red) fuzing and the use of solid-state components.


A typical Seaslug firing.

Some Seaslug test firings.

A firing that went slightly wrong.

Interception plots.


A few Seaslug pictures.





Contact Call!

Something different: Fireflash.

Some Seaslug statistics.

The three Seaslug firing modes.  

A glossary of Seaslug terms.



The background story of Seaslug.

Seaslug and the Candle Flame.

Early tactical thoughts on Seaslug.


The ships of the County Class.

Radar sets of the County Class.

Details of the Type 901 radar.

Seaslug in the Falklands.

The proposed re-activation of HMS Kent in 1982.




Some Seaslug tales and anecdotes.

Seaslug Myths and Legends.

Questions...and answers.

The Seaslug Tool Chest.


Fuzes for the Mk1 missile.

Proposed fuzes for the Mk2 missile.


Related links

Seaslug's stablemate -Bloodhound.


If you have any photographs, information or stories about Seaslug, I'd be delighted to hear from you.

Comments to:

Return to my home page.


I'd like to thank all those who have sent me pictures, information and assorted tales; and especially those in the Directorate of Naval Security and their successors in the Fleet Principal Security Adviser's office who made it possible; also the curator and staff at HMS Collingwood's Radar & Radio museum.  The views expressed, however, are mine alone and not of the Royal Navy or the Ministry of Defence -or anyone else for that matter.  I also lay claim to any errors in these pages; feel free to send any comments to:


Last updated 20th March 2015.

Copyright SR Jenkins, September 2002.