Warren Gatland announced a 37-man Lions squad on Thursday afternoon for this summer's tour of South Africa.
Gatland had initially been expected to name a 36-man group, down considerably from the 41 players he took to New Zealand four years ago.
The three-tour Lions head coach revealed that the extra player was one of the backrow members. Ireland's Jack Conan, back in form after a nightmare 2019/20 season, and Sam Simmonds - who hasn't played for England since 2018 - were two of the surprise inclusions in the backrow.
"We added an extra name," said Gatland.
"The squad, initially, was going to be 36 but we've gone to 37 to cover all our bases.
"Looking at our loose forwards, and the attrition, just getting an extra number there is a bit of a back-up.
"We wanted to keep the numbers down a little bit less than we have in the past. We felt that a 37-man squad, and getting permission from the board and the CEO to do that, is something we looked at yesterday."
Gatland added that selecting this Lions squad was "stressful".
"I have to be honest, in all my time in coaching, this is the hardest, most challenging squad that I've ever been involved with to pick," he said.
"It's about trying to get a balance, looking at who we're playing against.
"It hasn't been an easy decision. We had a meeting yesterday, it was about four hours [long] and we went through the squad, looked at all our options.
"When you're selecting a squad, there are a lot of factors to take into consideration. You're looking at form in the Six Nations, you're looking at players who have performed for you in the past, players that have performed at club level, won trophies and championships, and then you're looking at some younger players you feel that you can develop on the tour."