A 100-ball innings and a “wild card” 10-ball over – cricket in the summer of 2020 will look very different, after the England and Wales Cricket Board announced revolutionary plans on Thursday for its new city-based tournament, which it hopes will breathe new life into the nation’s summer sport.

The ECB pulled a major surprise when it announced that the new tournament that has divided opinion in the game will not be a Twenty20 competition as planned but a radical new format based around 100-ball innings, 20 balls fewer than Twenty20.

Teams will bowl 15 traditional six-ball overs with a wild card 10-ball over which could be used at any stage a captain deems it useful tactically. A countdown clock, showing how many balls are remaining, will be used and there will be a strict cut-off time. Full details are yet to be finalised and there could be further unique innovations, including scoreboards modified for the 100-ball concept.

Matches will be played in a five-week block during the school summer holidays with games starting at 2.30pm and 6.30pm. They will last three hours with eight to be broadcast live on BBC, the rest on Sky Sports.

Broadcasters were consulted on the new competition and gave it their enthusiastic backing. It is made for television cricket, a reflection of the fact the broadcasters have paid £1.2 billion for rights from 2020-2024.