2/1 Summer catch-up with awesome HS2 site visit (part 1), air traffic crisis, ULEZ and booking office rows

We're back!  Christian Wolmar and Mark Walker launch Season 2 bringing you up to date with three of the summer's biggest transport stories - air traffic control in crisis [1:49], Greater London's ULEZ extension [5:19] and England's main line rail booking office review [8:58] - including the take on the latter of ASLEF union leader Mick Whelan [13:51].  We then take listeners on the first part of our audio visit to the HS2 high speed rail line construction sites - this time the Colne Valley [19:30].  Christian finally asks what needs to be done to protect the 'turn-up-and-go' railway in Great Britain.