LONDON–Bellwether British retailer Marks & Spencer posted its worst underlying quarterly sales performance for three and a half years after the wettest April and June since records began hammered trade in womenswear. The firm, which sells clothes, footwear and homewares as well as upmarket foods, also said on Tuesday that the head of its non-food business Kate Bostock would leave the business, adding her name to a list of significant top management departures this year. Marks & Spencer (M&S) said sales at UK stores open more than a year fell 2.8 percent in the 13 weeks to June 30, its fiscal first quarter, in the firm’s worst quarterly drop in sales since the third quarter of the 2008/09 financial year. “General merchandise underperformed in a difficult trading season. We are confident we are taking the necessary steps to address this,” said Chief Executive Marc Bolland.