111579 F/L Wilfred Johnson 172 Sqn London Gazette 6 Feb 45 and its definitely a DFC. I doubt if this was for the single act of bringing his Wellington back, unless he had been involved in an action first. It looks like a 'non immediate' award, possibly at the end of his tour as there is no citation immediately available, which is often the case if awarded for a specific act.
Where's TTN when you need him!!
Old Duffer