Concentration of 60 vessels is sighted off Calais

Admiralty orders all cruisers, destroyers and small craft to be kept at immediate notice during darkness and all boiler cleaning to be stopped until further notice.

RAF issues Alert No. 1 ("Invasion immanent, probable with 12 hours").

All units in the Army's Home Forces were stood to and at eight hours notice to move and fight.

"Cromwell" issued

Deputy Chief of Staff at GHQ Home Forces issues the coded order "Cromwell" to Eastern and Southern Commands; IV and VII Corps (GHQ reserve); and HQ London District. It was repeated for information to all other commands. It took up to four hours to reach troops on the coast.

On receipt of "Cromwell":

  1. Troops were to take up battle stations
  2. Certain civilian telephone and telegraph lines were to be taken over by the military
  3. Liaison officers were to take up their duties with branches of the civil administration

In many cases the order was erroneously understood to mean that an invasion was in progress and church bells were rung.