Driving south from york on m1. still light outside, but cars were using headlights as starting to get dark. south east of the sky had cloud cover, south west was blue sky. not dark enough to see stars (was about 4:30pm gmt). both myself & partner see a very bright white/blue speck of light shoot across the sky south east to south west in front of us. it was faster than a shooting star speed, but as bright & about the same size speck in sky as a star. must have been below cloud cover as saw it from left to right in sky, from cloudy sky area through blue sky. couldn't see any type of trail left behind. seemed to be travelling at consistent height in sky. i waited until a few cars had gone passed with their light on & noticing none of their headlights had recreated the light i saw in the sky, i asked my partner if he had seen a bright light shoot across the sky a minute earlier. he was surprised, as he had seen it too & also thought he must have imagined it or would see it again & be able to explain it. neither of us saw the light again. we agreed it went incredibly fast, blink & you would have missed it. we couldn't explain what it could be.