Similar thing happened to me today. On our way to a DonMog member's funeral in the Morgan and approaching a roundabout on the A46 southbound near Leicester. A Ford Focus undercut me, went round the outside of one car, inside another, outside yet another and then inside again. I had been overtaking and was in the outside lane. As I was less than 800 yards from the roundabout, I was about to indicate and move left to be in the correct lane when it happened. Only just saw him in time.