Soze wrote:A one day thrash fest would easily work. The thing in 2003 that had Testament, Nuclear Assault and Death Angel (as well as a sprinkling of black and death metal bands...I think Amon Amarth and Marduk were on the bill as well?) would easily sell out a 2-4,000 venue in London. But an actual festival would struggle without booking the real big names.
I would argue it'd be safer and better in the long term to keep it in a venue around 1-1,500 to be honest; if you put it on in Brixton you would run out of headline bands too quickly. Megadeth and Slayer can already play Brixton without the need of this fest so you'd have to throw a lot of money at them to convince them to play at the fest and not as their own show. Other than that your left with Kreator, Anthrax and Metallica (if they want to specifically play the fest but you can't rely on that).
If you kept the fest smaller you increase the pool of headliners: Testament, Exodus, Anthrax, Overkill, Kreator, Coroner (if they get themselves together), Voivod and a reuinited Sabbat. So keeping it smaller would be more viable in the long term I'd think.