Eko4me, no, not that one but clearly the one to which Gums refers. I was at Cottesmore at the time of the first. In May 67 I was at Waddo. In the Cottesmore case it was 2045 GMT in the middle of Danger man. We debated waiting a few minutes until the end of the programme thinking it was just a regular no-notice generation and 10 minutes would make no difference.
IT was rumoured Fylingdales reacted to moonrise which had not been programmed in.
There was another daytime alert in '67 which might have been the one to which you refer, short lived and had less impact on me. I do know the QRA crews would not stand down until they received a relaxation message in the correct format.