* - Flotilla leader

1:600 HMS Obedient for the "O" class with 4" guns. Only "A" and "B" carried shields in the "O" class. © Andrew Arthur.

HMS Offa represents the 4.7" gun ships, in a very gaudy coat of paint. She had SW.272 RDF instead of a searchlight and re-shipped her after torpedoes late in the war. © Andrew Arthur.

This design was part of a prewar appraisal of destroyers, and was the product of the need for a fleet destroyer capble of all sorts of employment, but also to be armed with whatever weapons were available; hulls could be engined and built faster than guns to fit them with could be cast. There was also a strong train of thought that the destroyer was a far to unstable platfrom for adequate control, and a stabilising system was not yet perfected...
To speed construction - war economys were paramount - the hull and propulsion system of the "J" class was adopted, as was a single quad pom-pom and two banks of quad tubes. The 4.7" guns however, were mounted in single, manual mounts, four superfiring four and aft. AA defence was to be provided by four single Oerlikons, these being around in sufficient numbers to replace the pitiful 0.5" machine-guns, and it was decided to replace the after torpedo tubes with a single 4" AA gun. Four DC mortars and 60 DC's were shipped aft.
Despite being able to accomodate the above armament, a fresh hull design was prepared, and this showed considerable potential for improvements - in the RDF and asdic field, there being two 155kW turbo-generators and two 55kW and one 10kW deisel generators to provide ample power.
It was next decide to arm the class with two twin 4" AA, but these were in short supply, so the 4 single 4" AA were considered, and fitted to Onslaught and Onslow. However, to preserve class homogenity, they were transferred ot the 4" gun "P" class, and two as yet unarmed "P" class were transferred to fill the "O" class gap, and fitted with the 4.7" guns.
They weighed in at over 80 an up to 124 ( Onslow ) tons overweight, a sign of the stresses in the 'utility' destroyer hulls to come...
Lastly in the armament schemes, Obdurate, Obedient, Opportune and Orwell had their after tubes and "Y" gun removed, 60 mines added and 5 single 4" AA added (!).
Both types (4" and 4.7") had a Mk.II HA/LA DCT with AR type 285 RDF, and AW type 286 was carried at the masthead.
Wartime, the single 20mm's were replaced by twins, and a huff-duff loop ( HF-DF) was added to the foremast, apart from in Onslow and Offa, where a lattice foremast was stepped, and SW type 272 was fitted in the searchlight position.