From an interview with Tony Sheridan in 2002. Of course, the total interview is to be found here; The Tony Sheridan World Wide Forum
SEVERAL LIVERPUDLIAN ARTISTS, INCLUDING JOHN LENNON, COPIED YOUR HIGH-CHESTED GUITAR PLAYING AND YOUR WIDE-LEGGED STANCE ON STAGE. WHAT ARE THE ADVANTAGES OF PLAYING THE GUITAR LIKE THIS?
This position relieved pain (caused by the pressure of the guitar body on my bony lower ribs). It also looked like the early Elvis. The "wide-legged stance" was a preventive measure in two senses:
1) After fifteen beers one was less likely to fall off the stage.
2) There was less chafing at the crotch, caused by wet jeans (we sweated an awful lot) worn without underpants (musicians just threw the old unwashed ones away and couldn't afford new underwear on the pauper's salary we received in the clubs). Also, there were no facilities for washing anything, (including ourselves) anywhere in St. Paul's.
From this we deduced that the Germans only bought throw-away underwear. It also looked like the early Elvis. John assumed a similar stance for apparently similar reasons, plus the fact that Tony Sheridan knew more chords (mostly weird) than he did. Furthermore, he was anxious to stay on good terms with "the stupid twat".