A headrest fairing was added retrospectively to the Nimrod Is, to ease pilot strain during catapult launches. Aircraft from the later production batch were fitted with arrestor hooks. Experiments with the first of this batch, refitted with swept upper and lower wings, lead to the Nimrod II. As well as the swept wings, this had at first an uprated Kestrel II engine. Later, these were replaced with Kestrel Vs. Later Nimrod IIs had a slight increase in rudder area to improve spin recovery of inverted, float-equipped aircraft. Originally it was intended that the Nimrod II should have corrosion-resistant stainless steel, but only three of these were built. The first of 27/33 Nimrod IIs was delivered in March 1933.