By October, engagement rules were modified to allow engagement during the day and also against hostile aircraft. The maximum height that engagement could take place was lowered to 4,000 feet. Unseen aircraft could only be engaged if the order “Attack in progress” had been received. Seen aircraft could only be engaged if clearly recognized as enemy aircraft and observed to bear enemy markings or judged to be hostile by its actions, and its height was below 4,000 feet.
In order to minimize the risk to friendly aircraft, any aircraft that needed to approach the Diver Gun Strip from seawards below 4,000 feet, for whatever reason, was instructed not to approach on a direct line to London (this meant flying on a course as much north of 300˚ as possible) and at a speed not exceeding 285 mph. No target was to be engaged flying on a bearing north of 300˚ unless recognized as a flying bomb.
During the passage of bomber aircraft, 11 Group RAF Controller at Uxbridge could impose restrictions to unseen fire by informing the GORs. To protect other friendly aircraft, the Sector Commander, North Weald or RAF Forward Controllers had absolute power to impose any restrictions as necessary.
Sadly, despite these precautions, some incidents of “friendly fire” did occur. AA Command notes a total of two Mosquitoes and one Boeing being shot down in the Gun Strip during the period to Decemeber. One incident that has been fully documented by Collis & Barker involved a Mosquito from RAF Coltishall which entered the Diver gun Strip while pursing a flying bomb and was brought down in flames at Blundeston by HAA fire on Nov 14th. The aircraft was piloted by two American pilots attached to the RAF to gain night fighter experience and it is probable their inexperience is the reason why they entered the Gun Strip without taking the necessary precautions.
A high state of readiness was required at night when the Diver Gun Strip was in operation. When day time engagement was allowed, no specific state of readiness was specified, guns only opening fire if sufficient personnel were available. Personnel were not to be kept on site for this purpose and personnel resting were not to be disturbed.
The Air War Over Lowestoft, B Collis & S Baker, Lowestoft Aviation Society, 2011