had a accident in my car today.

going round a roundabout, i'm in the right lane, galaxy in left lane. heading onto a duel carriageway as i turn off the roundabout i get shunted in the passenger rear door and half spun round. we both stop and exchange details. he says it's my fault as i turned in front of him. i was exiting the roundabout onto the outside lane of the dual carriageway. he said he was turning right on the roundabout. surely if your turning right at a roundabout you would be in the right hand lane.