Lankshear, a £10m summer signing from Tottenham, scored the only goal of the game in the 61st minute.
Moses Itauma will fight for a world heavyweight title in his 15th professional contest.
The 23-year-old sealed victory on the second of two play-off holes.
Steve Borthwick’s team lifted their total of yellow cards for 2026 to 15 in eight Tests.
Flintoff was set to miss part of the team’s winter tour of South Africa due to a Big Bash League coaching role.
Well-related gelding has blossomed this year.