With a dash through their respective school exits, John and Paul would arrive together on the same stretch of street at the same moment and were truants for the afternoon - 'sagging off'. John would have his guitar ready.From a stop on Catharine Street, they boarded the 86 bus, a green double-decker like those driven by Harry Harrison, father of Paul's young schoolfriend George. They found their way upstairs and had a smoke, strumming strings while the bus bounced them out to the southern suburbs. Within thirty minutes of sneaking out, they were inside Paul's terraced council house at 20 Forthlin Road, empty in the daytime. As Jim McCartney would no more let Paul skip school than allow that boy in the house, subterfuge was vital. Afternoon sessions, two till five, ended with a hurried wafting around of smoke and washing of dirty dishes ... though by then they'd often written another song.