Stay up to date with notifications from The Independent Notifications can be managed in browser preferences. All News Sport Culture Lifestyle Southampton travel to Middlesbrough for the first leg of the Championship play-off semi-final tomorrow (Getty) Middlesbrough has lodged a formal complaint against Southampton , alleging that the club spied on their training sessions ahead of their Championship play-off semi-final tie. The English Football League (EFL) has initiated an investigation into the allegations, treating the matter as potential misconduct under its regulations. The complaint reportedly centres on a Southampton performance analyst who was caught filming and taking pictures of Middlesbrough's training at their Rockliffe Park base on Thursday morning. EFL rules explicitly state that no club shall directly or indirectly observe another club's training session within 72 hours prior to any scheduled match between them.…