Watson had appeared unsteady in the aftermath of the collision, failing in an initial attempt to stand from a kneeling position.
Jack Nowell replaced Watson as he was assessed for signs of concussion, but six minutes later, Watson jogged back on to the pitch and proceeded to play the remainder of the Lions’ 24-21 win.
Watson also played 72 minutes of the drawn series decider at Eden Park seven days later.
The recall element of the head injury assessment has since changed.
Instead of being asked to recall a set list of five words, with results compared to a baseline set when unimpaired at the start of the season, a random sequence is generated from a bank of 20 different words for each assessment.
Players are penalised for incorrect answers, meaning learning and repeating all 20 would result in a fail.
Watson’s fellow England wing Jonny May admitted in 2019 that, after a head knock in a game against Wales, he had tried, and failed, to pass the same part of the test by repeating words., external
Players are also tested on their balance and orientation, and have to pass all elements of the assessment to return to play.
Independent doctors also review video replays and data from smart mouthguards to review collisions. In rare cases they can overrule the results of an assessment if they still have concerns about a player’s performance in it or there was an error in administering it.
Whether players pass and return to action, or fail and are removed, they will continue to be assessed in the hours and days that follow.