"Careless leaving that question paper behind;but …

 The Governor admired clever Evans and his beautifully laid plan. He called it careless of him to leave the question paper behind. He observed that all criminals made mistakes somewhere. That is why they were nabbed. He hoped that very shortly Mr clever-clever Evans would be back inside the prison.

The text on the last page of German question paper contained the plan of escape. It had important clues of the route. From Elsfield Way the person had to drive to the Headington roundabout and from there to Newbury.
After sometime, Superintendent Carter informed the Governor on phone that McLeery had spotted Evans driving off along Elsfield Way. They had got the number of the car all right and given chase at opce. But they had lost him at the Headington roundabout. Since McLeery felt quite weak when they got to the Examination offices, they rang Radcliffe for the ambulances from there. They left McLeery on Elsfield Way. Thus, the injured McLeery, who had posed to help the authorities, disappeared and Evans remained untraced.
The other clues: Index number 313; Centre number 271 and ‘Golden Lion’ also had a deep meaning. The Governor took help of an Ordnance Survey Map for Oxfordshire. The six figure reference 313/271 brought him in the middle of Chipping Norton. He found Evans in the Golden Lion in Chipping Norton.