A severe slowdown in growth is causing an overdue shakeout of underperforming retailers. In recent years a consumer boom has helped oil the wheels of high street commerce, cushioning retailers from the full force of changes in shopping habits and unleashed by the growth of out-of-town and online retailing. But with consumer demand weaker and a host of cost increases eating into margins, a long overdue shakeout of weaker high street fascias is inevitable.