From Knox's website:

 

"(20 July 2009)
I'm playing acoustic at Rebellion (Blackpool), onstage at 3.50pm on Friday 7 August and will be joined on stage by Charlie Harper for a few songs. Hope to see you there!"

 

(17 Aug. 2009)
My solo gig at Rebellion (Fri. 7 Aug.) went quite well, the highlight being Charlie coming on and doing "Warhead" and "Cocaine" for the encore."

 

YouTube footage: 

 

Knox & Charlie's accoustic 'Warhead'

Click on the above picture to see Knox & Charlie playing Warhead