Toyota Supra 2.5l Twin Turbo (JZA70) - Fixing leaking boot

The problem

I was getting a lot of water entering the boot. I couldn't find the source of the problem. I resealed the rear lights but this didn't fix it. After a particularly heavy rainfall, I opened the boot and a large amount of water came from the boot lid itself.

The water was coming into the boot lid at the centre spoiler support

The solution

Remove the rear spoiler
 

You can see the rubber grommet that seals the centre mount to the body, but this appears to be part of the rear spoiler itself and can't be replaced.

I've used some black silicone sealant round the rubber and refitted the spoiler.