On 22 September 2010 at South Moreton, 165104 weaves across from the up relief to the up main line at full speed, after having bypassed Didcot on the east curve whilst working the 1P41 12:01 Oxford to Paddington First Great Western service. Although of course the Class 165/1s & 166s are virtually interchangeable, it was at one time usual for these fast services (this train stops only at Reading and Slough) to be operated by the Class 166s, while the Class 165 tended to be used for the stopping services. This distinction rarely applies nowadays. Both types have a 90mph top speed, but of course the Class 165s lack air conditioning.