Williams has confirmed that Paul di Resta has replaced Adrian Sutil as its official reserve driver for the upcoming Formula 1 campaign.
Di Resta spent three years racing in Formula 1 with Force India between 2011 and 2013, before losing his seat and returning to the DTM fold at Mercedes, having won the 2010 championship prior to his single-seater switch.
Di Resta will act as back-up to regular drivers Valtteri Bottas and Felipe Massa, with Williams having appointed Sutil last year in the wake of Bottas' back injury in Australia.
"I am delighted to be joining Williams as reserve driver and look forward to the 2016 season," said the Briton, who will conduct simulator sessions in order to ensure he is fully prepared.
"It will be a busy year combining both driving in DTM with Mercedes AMG, and attending the Formula 1 Grands Prix in my new reserve driver role.
"I will be giving my full support to both and look forward to the exciting possibilities the year has ahead. I would like to thank Williams for the opportunity to be part of the team."