 Fifteen engines were constructed according to this original design, but following the retirement of Thompson as CME, the remaining fifteen locomotives that were planned were immediately redesigned and ultimately emerged as Peppercorn Class A2.When Edward Thompson was appointed Chief Mechanical Engineer of the London and North Eastern Railway in April 1941, he envisaged a new standardisation programme involving ten locomotive designs including two Pacific types.These were an express passenger type (designated A1) with driving wheels and a 'heavy passenger and freight' type (designated A2) with driving wheels.