Business Green: The clean tech investment category’s good health was highlighted today after one of the world’s leading green investment firms pulled off a £104m IPO, blowing initial expectations out of the water and delivering the largest investment company IPO on the London Stock Exchange since July 2008. Impax Asset Management Group plc announced that it had completed the successful IPO of its Asian-focused subsidiary Impax Asian Environmental Markets plc, issuing 104,500,000 Ordinary Shares at a …