Another 'Retro Light Fit' Question

[Boddney]

I thought I'd go mad and spend £1.47 on a laser brake light from China just to see what it was like.

Ive noticed that on the motorway these days that older cars with bulb powered brake lights like mine seem to get lost in the sea of modern LED brake lights.

So this little thing is a laser that points down on the road and projects a red line on to the road surface. It also has the added benefit that because it's a laser, when there is a lot of spray it lights the spray in a red triangle shape from the unit to the road like the smoke gets lit at a rock concert. The question is, is it legal?

Just got it rigged in my garage at the moment and of course it's daylight.

Opinions please.