Defence Secretary Philip Hammond told ITV News it was not for him to judge whether Sgt Danny Nightingale should have been sent to prison.
He added that the Court of Appeal "acted swiftly" in this case which showed the system was "robust".
More top news
Nearly 38,000 runners will hope to complete Sunday's London Marathon making it the biggest event in its 35-year history.
Rain across central Britain with longer, intense downpours with thunder in places this evening. A lucky few will stay sunny and dry.
Planning on going to the London Marathon tomorrow? Read our handy guide first!