Paint over wall with multiple paint colours

[stripybadger]

The previous owners of my house had two colours on the wall (dark at the bottom, light at the top). I've painted over it (three coats of emulsion), but when the light shines on the wall you can see the line where the dark paint stops.

What's the best way to hide this?

If I just keep going adding more coats will it eventually disappear? I've seen 'obliterating paint' on sale, which sounds like what I want but most of them claim to be for bare plaster.

Thanks!

 

[Robbie uk]

Try putting a few extra coats just on the bottom to try and even things up.