Fairmile D motor torpedo boat
The Fairmile D motor torpedo boat was a type of British motor torpedo boat (MTB) and motor gunboat (MGB) designed by Bill Holt and conceived by Fairmile Marine for the Royal Navy. Nicknamed "Dog Boats", they were designed to combat the known advantages of the German E-boats over previous British coastal craft designs. They were bigger than earlier MTB or motor gunboat (MGB) designs (which were typically around 70 feet) but slower, at 30 knots compared to 40 knots.

Boats
The first twelve boats were ordered on 15 March 1941, becoming MGB 601 to MGB 612. The prefix was altered from "MGB" to "MTB" in September 1943.
Another 28 boats were ordered on 27 April 1941, as MGB 613 to MGB 616, and ML 617 to ML 640, although the MLs were quickly reclassed as MGBs. All (except early losses 622 , 631 and 639) were reclassed as "MTB" in September 1943. Eight of these were handed over to the Royal Norwegian Navy in 1942.
A further 60 boats were ordered on 18 November 1941, numbered from 641 up to 700, some with the "ML"prefix, others as "MGB" or "MTB", although all survivors later became "MTB". However, from No. 697 onwards, the boats were classified as combined "MTB"/"MGB"s.
Another 23 boats were ordered on 7 April 1942 as MTB 701 to MTB 723, and then 48 more on 30 August 1942 as MTB 724 to MTB 771.
Finally, 58 more were ordered on 26 March 1943 as MTB 772 to MTB 800, and MTB 5001 to MTB 5029 (although MTB 5027 was cancelled, the only Fairmile order not to be built).

History
Unlike the Fairmile B designs (many of which were built overseas), the "Dog Boats" were only produced in component form in Britain. Some were built for the RAF's Marine Branch for use in the long range air-sea rescue role for downed airmen. Altogether, 229 boats were ordered (and 228 built) between 1942 and 1945.

Many versions were produced or converted from existing boats; MGB, MTB, MA/SB, LRRC and post-war FPB.

Since the Fairmile D could be fitted out with a mix of armament that gave it the capabilities of both a motor gunboat and a motor torpedo boat, later-war examples were all completed with a heavy combined armament and universally classified as MTBs. By 1944, the MGB designation was largely dropped by the RN and most of the mid-war (earlier model) Type Ds which had survived were reclassified as MTBs even if they lacked torpedo armament. Mediterranean-based MGBs, however, seem to have retained their MGB pennant numbers to the end of the war. 

Two captured boats were put into Kriegsmarine service.

Today the D-type is a popular choice among boat modelers.

There are no known survivors, other than two abandoned wrecks, one in Chatham, England and the other in Ellingsøy, Norway.

See also
Fairmile A motor launch
Fairmile B motor launch
Fairmile C motor gun boat
Fairmile H landing craft
Steam gun boat
Coastal Forces of the Royal Navy

Notes

References
 Friedman, Norman, British Coastal Forces: Two World Wars and After. 2023, Seaforth Publishing 
 Lambert, John. Fairmile D Motor Torpedo Boat.  (Anatomy of the Ship series) 1985 
 Lambert, John and Ross, Al. Allied Coastal Forces of World War Two, Volume I : Fairmile designs and US Submarine Chasers. 1990. 
 Konstam, Angus. British Motor Torpedo Boat 1939–45. (New Vanguard). Osprey 2003. 
 Konstam, Angus. British Motor Gun Boat 1939-45. (New Vanguard) Osprey 2010 978-1849080774
 
 North, A. J. D. Royal Naval Coastal Forces 1939-1945. 1972, Almark Publishing Co. 
 Reynolds, Leonard C. Motor Gunboat 658: The Small Boat War in the Mediterranean. 1955/2002.

External links

 Coastal Forces And Communications with France Before D Day 1944
List of Motor Torpedo Boats at unithistories.com

Military boats
Ships of the Royal Navy
Motor torpedo boats of the Royal Navy
Patrol boat classes
Auxiliary search and rescue ship classes
Gunboat classes
Torpedo boat classes