Had this act of vandalism on my Octavia, which is finished in brunello rosso, for a while now. Someone on here recommended the P1 nanocomposite polish, so I gave it a go using this polishing pad from Halfords:

 

 

Here's the scratch before:

 

 

And here's the same door panel after:

 

 

Not completely gone but a massive improvement and perhaps as good as I'll get it. I used a run of the mill microfibre cloth to buff it off.

 

Had previously tried T-Cut which proved to be completely useless. I'll wait a week and see if it still looks as much of an improvement.

It's a pretty good product to be fair, and I've had similar results, and seen similar results.

 

Works great by hand and is supposed to work even better by machine.