oh dear - HS2 again criticised as "nonsense", "truly daft", rich man's vanity project, etc.
let's get this straight. the current network - in particular the west coast route - is now so traffic heavy that it's on the verge of seizing up on a daily basis. virgin have extended all their trains, that capacity is full; subsequently they declassified one first class coach on each train, that capacity is full. the last infrastructure upgrade of the WCML (which isn't finished yet) was meant to future proof capacity until the 2020s but that too is already full. some of the slow trains were speeded up to create an extra train path, those trains are now full and standing all day, every day. that's not to mention the burgeoning freight sector which is now on a plateau because there are no more paths available.
so what to do.... upgrade the existing line? nope, the 20 further years disruption this would entail would be politically unacceptable, bearing in mind the improvements this would create would be at best marginal. there are 2 other non HS2 solutions that would create more capacity but both would be equally unacceptable - that is, make all trains including freight run at the same speed (60mph), but that would involve journey times that would double overnight; or eliminate slow freight trains by permitting 80T trucks on the road, but i don't believe that would be environmentally acceptable.
no. the only way to provide more capacity is new build. HS2 would reduce traffic on existing lines and provide the additional capacity for commuter services and freight that's needed right now, never mind in ten years.