BBC claims the sun'll last until about 1PM over here, and it won't start raining until 4.
Same thing happened on my ride yesterday.. It was beautifully sunny, so I set out for a 30 miler. Reached the 15 mile point, at which point the beautiful sun turned into torrential rain which lasted for the last 15 miles. The roads were like cycling through one huge never ending puddle, with no guards.
My clothes/saddlebag/shoes/hydration pack still haven't dried out.