The A1 has closed just an hour after reopening. Drivers are waking up to find the A1 is shut in both directions between the A607 near Grantham and Little Ponton junctions, with traffic being routed through Grantham. Police are dealing with a report of a concern for safety and the road is expected to be closed throughout rush hour. A serious accident last night near Colsterworth led to the closure of the road, until around 5am this morning. An air ambulance landed on the carriaeway.