In 1938 in a debate on ARP issues in the Commons it was stated that the estimated time between an air raid warning being sounded and the first bombs dropping would be between seven to eight minutes. This was one reason why at the time the government favoured lots of small shelters close to or in dwellings rather than larger communal ones that could take longer to reach and would be difficult to fill safely in so short a time. Does anyone know what the actual warning to bomb drop times were in 1940 - 1944 (excluding V2s etc)?
Very interesting This was about the time to kill street lighting length of warning required when enemy aircraft spotted 6. If the tests confirm the figure of 15 miles, the next and crucial question is whether a reliable warning can be given in time to enable the street lighting to be extinguished before a hostile aircraft arrives within that distance. 27. Allowing six minutes for the maximum time which the aircraft would bake to cover these 15 miles, two minutes for the process of extinguishing the lights and a further two minutes as a safety margin, the length of warning should be not less than ten minutes. 28. To this must be added the time taken to convey the warning of approaching aircraft from the point at which the aircraft is detected through Fighter Command to the lighting control points. We are informed that under the existing warning system this might be as long as 12 minutes. 29. The 22 minutes margin thus required (10 minutes warning plus 12 minutes for its conveyance) would theoretically coincide with the " Yellow Message " which was originally based upon a similar 22-minute period. We do hot consider, however, that, except perhaps in areas remote from the regions of active operations, the " Yellow Message," as at present operated, would offer a. sufficiently reliable medium for the transmission of the important " Lights Out " signal, upon the reliability and the timely receipt of which the whole safety of the proposed new street lighting scheme depends. 30. Moreover, the longer the period of the warning the larger is the area which would have to be placed under warning. If, therefore, the period were as long as 22 minutes, large areas of the country would, even in a phase of less intense air activity, get little or no use from the additional street lighting. AIR-RAID PRECAUTION POLICY. (Hansard, 16 February 1939)
A little odd - the timings and distances are those that pertain to warnings from sound location and not RDF (Radar) and are echoed (no pun intended) by the reports on the Malta sound mirrors. I suspect that either RDF was still so secret that no mention was to be made in public or hon members/noble lords were behind the curve. What is odder is that by this time it had already been recognised by the government that its original scheme of switching off street lights on the approach of bombers was unworkable but not for the reasons in Hansard. The original assumption was that any bomber attack on the UK would come from the East across the North Sea. It was intended to split Britain into zones ( first three but later revised to two). The Eastern zone would observe a dusk to dawn complete blackout from the outbreak of war but the Western zone would only switch the street lighting off on the approach of bombers. RDF should give enough warning time for this. However representations from municipal authorities and the electricity industry convinced the government that the switching systems were so unsophisticated and distributed that a complete simultaneous turn off of all the lights could not be performed from the control points. Some lights would stay on too long. The zoning scheme was abandoned and a countrywide black out substituted. The first city to go dark on the day war was declared was Glasgow. I wonder if the debate reported in Hansard was part of an early piece of misdirection. Marc Patrick Wiggam, The Blackout in Britain and Germany during the Second World War, PhD thesis, University of Exeter, 2011
