Graeme Smith has shocked teammates, Cricket South Africa and the wider cricket community by announcing his retirement.

Smith’s 347-match international career will end after the Test series decider against Australia in his home city of Cape Town.

The Proteas captain informed teammates of the decision at the end of play on day three, when Australia held a 234-run lead with all 10 wickets in hand.

“This has been the most difficult decision I have ever had to make in my life,” said Smith, the most-capped Test captain in history.

“It’s a decision that I have been considering since my ankle surgery in April last year.

“I have a young family to consider, and I felt that retiring at Newlands would be the best way to end it because I have called this place home since I was 18 years old.”

Smith’s form has been on the wane, and his average of 8.4 during this three-Test series with Australia reflected a batsman that never looked overly comfortable in any of the five innings.

But most pundits had expected the 33-year-old to lead his nation at the one-day World Cup in Australia and New Zealand next year.

Smith spoke of what a “good place” he was in during the pre-match press conference for the third Test, and with confidence that runs were around the corner.

Proteas coach Russell Domingo was similarly upbeat.

“Graeme’s record speaks for itself. It’s very seldom that he goes through a series without making a contribution with the bat,” Domingo said of Smith’s form in the lead-up.

“So it’s not something I’m too fazed about.”

AB de Villiers is the Test side’s vice-captain and most obvious successor, although Faf du Plessis is skipper of the national Twenty20 team and his leadership is highly rated in the country.

Cricket South Africa chief executive Haroon Lorgat admitted Smith’s decision came as a surprise.

“We must respect him for deciding to call time,” Lorgat said of Smith, who has helped keep his side No.1 in the ICC’s Test rankings since August, 2012.

“He would not have taken this decision lightly or without a great deal of thought.”

A World Cup win and home Test series victory over Australia are the only two major accolades missing from Smith’s reign as captain – which dates back to 2003.

Barring a staggering collapse from the tourists on Tuesday, it is highly unlikely he will achieve either.