Distorted picture e/w on grundig wf70 3020?

I have just inherited (literally) a grundig wf70 3020. The picture on the screen is completely rectangular and fills everywhere it should, however!, any picture that contains vertical straight lines, eg a building, starts to curve as it moves towards the edge of the picture. Anything at the edge that is curved straightens as it moves to the middle of the screen. Its a bit like watching one of those funny distorting mirors at the fair. I am led to believe that the tv worked perfectly until someone messed with the settings. So does anyone know if this is a setting fault or a hardware fault. It doesnt help that there is no manual!!! When googling I have found requests for service codes for e/w curvature (not sure if this is the same thing or if their picure was not rectangular) but no locations so if thats the problem, a direction or idiots guide would be great.