HAL have advised about a 20 minute hold to arrival, and adding up the numbers, about a similar hold for departures too.
12:55 BST final arrival, or 13:00 depending on runway.
13:00 hold to departures.
Red Arrows will transit over LHR between 13:06 and 13:09. 70 aircraft in all, to restore the truncated version on His Majesty's Coronation.