The Eden Sessions have surprised punters on so many levels over so many years and so many gigs – but The War on Drugs may have produced the most underestimated show in all that time. The announcement that the American indie legends would headline between the biomes arguably had the most low-key reception in some time. But we should've all learned by now not to doubt the Eden Project team's wisdom in this respect. Yes, this year's opener Lionel Richie was a no-brainer and banker – the man always draws a crowd and puts on a memorable night. Second star…