This is rare but does happen... The Diversion is simple
Stay on the M1 as if you are heading to Leeds, take the first slip off then tight left, A656 then left onto the A63 later, next roundabout right and then later left which will bring you back onto the A1 at junction 42. You shouldn't loose much time, maybe 2 minutes tops.
Junction 43 to Doncaster a1/M1 split.
Moderator: jeffw