Shoe producer and key supplier to Marks & Spencer, Lambert Howarth, has swung to a first half profit as it was boosted by a surge in orders during the revival of the UK high street giant. The London-based company, which generates about three-quarters of its sales from M&S and has enjoyed a jump in demand for its ladies' shoes, posted a pre-tax profit of £1.8 million after one-off costs compared with losses of £5.2m in the year-ago period.