Head coach Warren Gatland has selected a 41-man squad for the 10 fixtures culminating in a three-Test series against New Zealand, including surprise call-ups for Ireland full-back Jared Payne, England wing Jack Nowell and Wales back row Ross Moriarty. Four years on and now a test captain, the hooker was judged on his playing abilities alone but was overlooked in favour of three rivals - Ireland's Rory Best, Wales' Ken Owens and Jamie George, Hartley's understudy for England.
The inspirational back-row stepped down as skipper of his country in January but will have the honour of becoming only the second man to captain the Lions on two tours - emulating Martin Johnson's feat.
"Even the 2013 tour hasn't sunk in, ' said the flanker".
The squad includes 16 Englishman, 12 Welsh players 11 Irishmen and only two Scots. Scotland have not had a Lions test starter since prop Tom Smith in 2001.
The Lions have won just one series in 11 trips to New Zealand, 2-1 in 1971, and were demolished 3-0 on their last visit in 2005 by a rampant All Blacks side led by Dan Carter.
Owen Farrell was included as a flyhalf, alongside Dan Biggar and Jonathan Sexton, whose Ireland halfback partner Conor Murray faces a fight to overcome a nerve injury to take his place alongside Rhys Webb and Ben Youngs in the battle for the number nine jersey. "That's what makes us pretty excited about the quality of the squad going to New Zealand".
"There is competition for places and there will be players fighting for test spots with no clear number one, number two or number three in certain positions", Gatland told reporters.
"This will be the toughest tour".
"The midweek games tend to be a little easier but the quality of the opposition will be hugely challenging which is why we've selected a few more players than 2013".
Warburton, who was Gatland's captain for Wales from 2011-16, found out he was being retained in the role when he got a phone call from Gatland as he sat in his vehicle at a supermarket waiting for his girlfriend to return with the shopping.
Warburton is now out injured, and stood down from the Wales captaincy this year, but said he would be 100 percent fit. I was in a supermarket carpark and didn't believe him at first.