YORK S Joseph Rowntree Theatre is planning a day of celebrations on Wednesday to mark the 150th birthday of the theatre s founder - philanthropist and social reformer Seebohm Rowntree. There will be a fund-raising champagne tea in the afternoon, followed by a party for invited guests from the theatre and civic world in the evening. As well as being the founder of the Joseph Rowntree Theatre, Seebohm - who was the son of Joseph Rowntree - was the saviour of the Theatre Royal in the 1930s. He was also well known for his philanthropy and involvement in politics. A friend of Lloyd George, he wrote pioneering studies of poverty in York which ultimately helped pave the way for the modern welfare state.