Ivan Lendl has said there were "many factors" behind his decision to link up with Andy Murray for a second time, rather than one single reason.
World number two Murray won the US Open and Wimbledon - to date his only grand slam titles - with former world number one Lendl as his coach, before the pair mutually agreed a split in 2014.
The Briton subsequently linked up with Amelie Mauresmo, only for that partnership to end prior to this year's French Open.
And Lendl's return to the Murray team was duly announced on Sunday, with the 29-year-old stating he hopes their alliance proves a lengthy one.
"Andy and I have talked over the last few years," Lendl told BBC Sport.
"We've stayed in touch, and as you know, we parted on good terms.
"Everybody asked me what was it that made you do it, and I can't answer that. I really don't know, there are so many factors in there. I can't say what changed it from 'not really' to 'yes'.
Lendl watched on at Queen's on Tuesday as Murray began his defence of his title at the grass-court event by beating Nicolas Mahut in two tie-breaks.