Web Summit chief executive Paddy Cosgrave engaged in toxic conduct, waged a campaign of intimidation and attempted blackmail against his former friend and business partner, and torpedoed outside investment in the tech company out of fear he would lose control of the business, according to claims made in new legal proceedings. David Kelly, a former director and co-founder of the tech conference, is suing Cosgrave, the majority shareholder, alleging a complete breakdown of relations. He claims the tech entrepreneur, a former school friend from Glenstal Abbey, has oppressed him as a minority 12 per cent stakeholder. The CEO is alleged…