PUBLIC HEALTH RESEARCH VOLUME 2 ISSUE 7 DECEMBER 2014 ISSN 2050-4381 DOI 10.3310/phr02070 Putting Life in Years (PLINY): a randomised controlled trial and mixed-methods process evaluation of a telephone friendship intervention to improve mental well-being in independently living older people Daniel Hind, Gail Mountain, Rebecca Gossage-Worrall, Stephen J Walters, Rosie Duncan, Louise Newbould, Saleema Rex, Carys Jones, Ann Bowling, Mima Cattan, Angela Cairns, Cindy Cooper, Elizabeth Goyder and Rhiannon Tudor Edwards