A worker poses with the new Nokia Lumia 925 at its launch in London yesterday. Nokia unveiled a lighter, metal model in its Lumia smartphone range as it tries to catch the eye of buyers to close the huge market lead of rivals Samsung and Apple in the lucrative handset market. The new phone will be rolled out globally starting in June, and is due to be sold in the United States by T-Mobile and in China by China Mobile and China Unicom.