https://www.motorsport.com/f1/news/mcla ... f-1064036/
For me it's quite shocking news. Given his experience and capabilities, I consider James Key as a strong pillar for TR, but this move is completely understandable, since TR will always be just RBR's junior team.
Although unfortunate, clearly this will be a step up for him, since McLaren are in a better position to provide him a platform where to grow, and I'm pretty sure he'll make a big difference.
Not to mention that he's British and this will allow him to be closer to home and to his family more often.