While not as famous as the Avro Lancaster, the Handley Page Halifax was developed to the same specification as the Lancaster's predecessor, the Avro Manchester, and suffered similar engine-related issues. However, once the early Rolls-Royce Merlins had been replaced with Bristol Hercules air-cooled radial engines, the bomber's performance and reliability were transformed. The Halifax accounted for around 40 per cent of the RAF's total heavy bomber fleet throughout the war, with production coming out of Handley Page at Cricklewood and Radlett, as well as English Electric at Samlesbury and Rootes Securities at Speke among other manufacturers located across Britain. After the engine change in 1943, the Halifax became a valued and reliable stablemate of the Lancaster, equipping two major Bomber Command Groups, including Canadian squadrons, and specialising in glider towing and maritime reconnaissance.Handley Page Halifax: Second World War Strategic Bomber is a comprehensive assessment of the aircraft, covering its design, production, testing and RAF service, both as a bomber and in its other roles.