The British anticipated an attack by Japan, somewhere in the far east, well in advance of the attack on Pearl Harbor. Canadian troops were dispatched from Vancouver, by ship, in early November of 1941 to reinforce the British garrison on the island of Hong Kong. They arrived in late November, about 10 days before Pearl Harbor. On December 8 (the same day as Pearl Harbor ... but a day later, per the Int'l Date Line) the Japanese launched an attack from mainland China on the British garrison protecting Hong Kong. The British and Canadian troops, without any back up or re-provisioning whatsoever, held out 'till December 25 Xmas morning, before surrendering.
There is no doubt that Churchill knew the Japanese were poised to attack somewhere in the western Pacific ... there is nothing to indicate the British had intelligence indicating the Japs were going to attack Pearl Harbor first. Anything to the contrary is pure bunk pushed forward by Monday AM historical revisionists & journalists.
I suggest you read "Day of Deceit" by Robert Stinnett. It's an eye-opener. The U.S. had intercepted and decoded both military and diplomatic intercepts that provided the precise location and date of the attack. None of these intercepts were provided to Admiral Husband Kimmel and Lt. Gen. Walter Short in Hawaii.
Roosevelt bated the Japanese into the attack and then withheld vital intelligence information. He knew an attack against America by Japan, Germany's ally, would rally popular support for America's entrance into the war against Germany. In an effort to preserve FDR's sainted image, the mainstream media has gone out of its way to bury this story.
-Un-PC
Check out the following web location:
http://www.independent.org/tii/news/001207Stinnett.html