The Power Unit included in these Sets gives the game away! It is a 'Mainline Railways' item. Palitoy the owners of Mainline Railways took over the Airfix range of ready to run items in 1981 and absorbed them into their range. There were rumours of large stocks of the Airfix Blue Boxed items remaining in Store. The introduction of this style of Set still under the GMR banner was to help reduce the number of surplus items.