Edison International, the US utility company, has put up for sale some of Britain's biggest power generating assets, including two hydro-electric power stations in Wales, as part of a £1.5bn disposal plan. The giant Dinorwig hydro-electric power station, its neighbouring Ffestiniog plant, and a stake in Derwent, a natural gas plant in Derby, are being sold by Edison Mission Energy, the energy arm of Edison International. The company has hired Credit Suisse First Boston and Lehman Brothers, the investment banks, to advise on the sales which include assets in Spain, Italy, Australia and New Zealand. The entire portfolio is expected to fetch over £1.5bn.