Handley Page were initially disappointed with the performance of the Halifax which was below their predictions, much of this was because they had under estimated the aircraft's drag. Another contributory factor was Handley Page sticking to the 100ft maximum wingspan originally demanded by the Air Ministry's P13/36, the Halifax originally had a span of 98ft 8in whereas Avro did not adhere to that with the Manchester MkIII (i.e. the Lancaster) at 102ft 0in. The Mk III Halifax had a wider span of 103ft 8in and had significantly improved performance. Arguably the Merlin engine did not suit the Halifax as much as the Hercules (fitted from the MkIII on) which suited the Halifax better both aerodynamically and power wise.