England are trialling a system where coded information is passed from the team's performance analyst to captain Eoin Morgan during their limited-overs matches against South Africa, vice-captain Jos Buttler said.

England analyst Nathan Leamon had placed a series of numbers and letters on clipboards on the team's dressing room balcony to give Morgan suggestions for the on-field match-ups during South Africa's innings in the third T20 win in Cape Town on Tuesday.

The tourists have cleared the use of coded messages with the match referee and anti-corruption officials.

"(Leamon) was calling out the EuroMillions numbers - the lads were checking their tickets!" Buttler joked after the match.

"Seriously, analysis has become such a huge part of the game," he told Sky Sports.

The England and Wales Cricket Board described the system as a "live informational resource" that Morgan could choose to use or ignore on the field.

"Eoin is one of the best captains in the world, a fantastic, instinctive captain, and there's a nice balance going on," Buttler said.

"You have to be careful how you use the information best - there still has to be an instinctive, intuitive side to the game but if you can use analysis to better that then it is a force for good."

Victory at Newlands completed a 3-0 series sweep for England and sent them to the top of the International Cricket Council's T20 rankings.