Generally regarded as the finest bomber of the second world war the Lancaster arose pheonix like from the failure of the Avro Manchester. On 18th April 1940, Roy Chadwick the chief designer at Avro's proposed various changes to the Manchester including a variant powered by four Rolls Royce Merlins. An incomplete Manchester was taken from the production line in mid 1940 and modified to take four Merlin's by increasing the wingspan by 12ft. The first prototype was flown on January 9th 1941 and it was found almost immediately to be a war winning weapon. Manchester production was phased out to be replaced by the Lancaster. In fact the initial Lancaster production batch were converted from Manchester's on the production line.
The first squadron to receive Lancaster's was No44 (Rhodesia) squadron which carried out its first operation on March 3rd. On the 4th April 1942 Lancaster's hit the headlines for the first time when 12 Lancaster's of 44 squadron made a daring low level daylight raid on the MAN diesel factory in Augsburg. Unfortunately Me109's of JG2 got amongst the Lancaster's and only five aircraft returned home. The factory however was very heavily damaged. It was as a night bomber however, that the Lancaster is most usually associated and from 1944 more or less replaced the Stirling and Halifax as the pre-eminent 'heavy' in Bomber Command. With the introduction of electronic blind bombing aids from 1942 alongside the introduction of the Lancaster such as GEE, OBOE, H2S and G-H, night bombing became steadily more accurate and deadly.
Although the Lancaster did not change very much during it's production life, the Lancaster II was developed powered by Bristol Hercules radial engines. This move was prompted by fears that production of the Rolls Royce Merlin would not be able to meet demand. In the event, the Packard Motor Company in the USA began license building the Merlin which was to power the Lancaster III and the shortage never materialised. Within Bomber Command Headquarters the radial engined Lancaster II was not popular as the Hercules guzzled petrol, especially at high altitudes and for deep penetration raids the Lanc II had to sacrifice bomb load for fuel. Only 300 of the Lancaster II were built exclusively by Armstrong Whitworths in Coventry, (where my father worked as a matter of fact).
Although it is not possible to describe the many operations that the Lancaster took part in, the reason for the aircraft's success was it's ability to carry ever increasing loads of greater weight and versatility. For example the Lancaster could carry three times the bomb load of the American B17 to Berlin. Furthermore, because the Lancaster's bomb bay was a huge open space the Lanc could carry an extremely wide range of weaponry ranging from the 12,000 HC bomb to an all incendiary load. Typically a Lancaster would carry a 4000lb or 8000lb 'Cookie' with the rest of the bomb bay occupied by smaller bombs and incendiaries. Finally the Lancaster was modified to carry the 22,000 lb 'Grand Slam' earthquake bomb which was the largest bomb delivered during WW2. In 1944 Three Group, converted from the Stirling to the Lancaster. In doing so they were equipped with G-H an extremely accurate airborne blind bombing aid similar to Oboe. G-H equipped Lancs often had brightly coloured fins so that other Lancs could formate on them during the bomb run.
All in all 7,377 Lancaster's of all marks were built with production being undertaken by Avro,