Guardiola made Rodri one of his main summer targets after identifying him as the long-term replacement for ageing Brazilian worldwide Fernandinho.
Simeone fought until the end to get Rodri, who only signed from Villarreal last summer, to say, but in the end the player has preferred to start a new adventure in the Premier League, where he will play under Pep Guardiola.
Manchester City's previous club record was the £60 million they paid Leicester for Riyad Mahrez in 2018.
His release clause was €70 million and with that out-of-the-way, there's next to nothing stopping Manchester City from signing the midfielder.
"In this way, the player has unilaterally terminated the employment contract that bound him to our club until June 30, 2023".
Atletico have done well on Rodri financially speaking.
City also missed out on Jorginho last summer and were previously interested in Fred prior to his move to Manchester United. "Few people read the game alone".
Rodri has only spent a single season at Atletico Madrid, having been a €20m purchase from Villareal. He moved back to Atletico 12 months ago and made 47 appearances in all competitions last season, including 34 in La Liga as Atletico finished runners-up to Barcelona.
Manchester City are also preparing to announce the signing of PSV Eindhoven left-back Angelino after they activated the buy-back clause inserted in the defender's contract.