That did not affect his immediate commitment to City, nor dull his relentless appetite for success. What followed was a phenomenal 2017-18 season in which City won the Premier League with a record 100 points and they built on that by claiming an unprecedented domestic treble the following year.

Yet, having taken a year's sabbatical between his spells with Barca and Bayern, it was clear the famously intense Guardiola did have times when he wished to step away from the pressures of the game. It would not have been a surprise, therefore, had he walked away again once his contract ended.

However, as he reaches that landmark birthday on Monday, Guardiola is still in the hotseat at City and, after twice renewing his contract, looks set to continue for some time yet.

"Before I thought I was going to retire soon, now I'm thinking I'm going to retire older," he said earlier this month, fresh from committing himself to the club until the summer of 2023.

Indeed, when he reached the milestone of 700 games in management in December, he even suggested he might only be halfway through his career.

"Seven hundred games – I'm going to do 700 more and after that I'm going to retire," said Guardiola, who has won 29 major trophies since setting out as manager of Barcelona B in 2008.

"When you start you don't expect what will happen in the future, so it is good to have 700 games and so few defeats."

There is little doubt Guardiola has been a phenomenal success. The "tiki taka" brand of football he oversaw at Barcelona led to a golden era in the club's history. Their slick, possession-based game built around Lionel Messi, Andres Iniesta and Xavi, coupled with high-intensity pressing, made them an outstanding unit. In just four years they won three LaLiga titles and two Champions Leagues, among other successes, and were the envy of the world game.

He successfully transposed the formula to Bayern, where he won another three league crowns and he adapted it again at City, although it took him a year to fully bed in at the Etihad Stadium.

There were detractors when he arrived in England. Some questioned whether his style could really work in the "tougher" Premier League where there were other clubs with equally competitive squads.

The first season added weight to their argument as City scrambled into third place but Guardiola stuck to his footballing philosophy and was fully vindicated over the next two seasons.

Admittedly, he did benefit from the club's spending power as he reshaped the squad but it was not just the results that were outstanding, but the manner in which they were achieved. The football was exhilarating as City smashed record after record in 2017-18 – including most wins, most points and most goals among others – and standards barely slipped the following year.

The only difference by then was that Liverpool had responded to their raising of the bar and almost matched them, finishing runners-up by just a point. Jurgen Klopp's side then maintained the standard and won the title in 2020 as City, as they inevitably would have done at some point, let their intensity slip a little.

The formidably driven Guardiola will no doubt ramp that up again and target further glory, although the current season could be difficult to judge given the impact of the coronavirus pandemic on the game and the challenges it has presented.

The one blot on Guardiola's City career to date as been his failure to get beyond the quarter-finals of the Champions League. There is little doubt winning Europe's top club competition has been the club's chief aim since hiring Guardiola and was the main reason for his appointment.

He has won enough otherwise to ensure his reign will not stand or fall by it, but it remains the top objective. Guardiola is now judged by the highest of standards and his work at the club may not be considered complete by some until he achieves it.