How to prevent light from coming in around the edges of black out blinds

Adding an update to Peter Mounce's answer from: https://zebbakes.com/2011/06/21/how-to-uninstall-a-velux-black-out-blind/

The Mr McDonald method at the end worked for me in a couple of seconds, and doesn't have the crazy screwdriver involvement. The quote is:

spoke with a very helpful chap at Velux (UK) and removed the blind quite easily. Method was this: 1) With the blind retracted fully, grasp the casing firmly at each end with your fingers at the back (between casing and glass) and thumbs on the front. 2) Now twist/rotate the case up and out (as if twisting case toward top of window frame) and listen for the ‘click’ of the catches releasing both sides. 3) When both catches released – blind should slide forward and out! Tried it and it worked a treat! Obviously no guarantee but was reassured by Velux that if the clips should break on attempting removal that they can supply a new set of brackets for re-installation.

If your room is upstairs, have your blinds tilted upwards; the opposite if downstairs. At night, turn on your lights and slant your blind the way you like and go outside and see how little you can see (if at all). Having bigger blinds will make it so there are fewer gaps but still the angle is the main issue.

I doubt if the neighbors really pay too much attention unless they are very nosy. If you are doing your best to close the blinds and they still are annoyed, that is their problem.

As far as legality, you are closing your blinds and what you do behind closed doors is your business.

All the best.