Dave,
It seems to only be politicians that are so certain who it was. Maybe they are all taking lessons off Gove the viper and disregarding what experts say?

Or maybe they know more about it than you do.
It is not just British politicians, but the governments of every EU nation, plus Canada, Australia and all the other well informed liberal democracies in the world.

Perhaps you think it is some vast global conspiracy of lies?
Perhaps you think you know more about it than all of them?