Martinsyde A.D.C. 1, Martinsyde A.D.C. Nimbus & Martinsyde F.4A

The Martinsyde A.D.C.1 was a development of the Martinsyde F.4 Buzzard made by the Aircraft Disposal Company that bought Martinsyde's stores when it went into bankruptcy in 1922.
John Kenworthy decided to fit an Armstrong Siddeley Jaguar engine delivering 380hp of power into the airframe of a regular Buzzard and retaining the original armament of two 0.303in Vicker Machine guns in the front. The first prototype flown for the first time on 11th October 1924 and it took part in the 1925 and 1926 King's Cup Races. It attracted some foreign interest when Latvia's Air Force ordered eight airplanes in 1926 that were delivered the same year. At least two of them were still active in 1938.
The Martinsyde F.4A was a two-seater conversion of the Buzzard that most of them served with the Spanish Aeronáutica Naval and Aeronáutica Naval Republicana (Naval Aeronautics and Republican Naval Aeronauticrespectively). They were bought in 1921 and assigned to the El Prat pilots school, in Barcelona and later, they were assigned to the San Javier aeronaval base, in south-eastern Spain. They were in active trainer role until 1936 when the Spanish Civil War started.
The Martinsyde A.D.C. Nimbus was a further development of the A.D.C.1 made by John

The Martinsyde ADC Nimbus

Kenworthy using a 330hp Nimbus six-inline water-cooled engine. It was basically the same airframe of the Buzzard with a modified vertical tail, a horn-balanced rudder and revised aft fuselage decking. It was going to be armed with the typical pair of 0.303in Vickers Machine guns but they never were installed. Two prototypes were completed in 1926 which took part in the King's Cup race of that same year and, one year later the first prototype was modified with faired undercarriage legs and cylinder head fairings. It didn't attract any interest and therefore no orders were placed. As we couldn't find any side drawings of blueprints of this airplane, we left it undrawn.

Sources:
1. https://en.wikipedia.org/wiki/Martinsyde_Buzzard
2. http://www.aviastar.org/air/england/martinsyde_adc-1.php
3. http://www.aviationcorner.net/gallery.asp?pg=45&fp=37&airline=Espa%F1a%20-%20Arma%20A%E9rea%20Armada&sort_order=votes&set_lang=true (translated)
4. Salamander Books - The Complete Book of Fighters