Catt, the England backs coach, was born in Port Elizabeth before uprooting to Bath and he toured South Africa twice with his adopted country, in 1994 and 2000, so has been able to forewarn Mouritz Botha and Brad Barritt about the kind of abuse they can expect to receive on their return to the country in England colours.
But with an inexperienced England squad arriving in Durban on Thursday, Catt admitted no words can accurately prepare them for what is awaiting them on the rugby fields of South Africa: "You can't prepare for it. You have to feel it."
Catt, who won 75 caps for England, added: "Stuart Lancaster has been sending emails for the past three or four months saying 'prepare yourself, prepare yourself, prepare yourself'.
"Brad Barritt did a presentation for us in connection with what to expect from the country and what to expect from the people - but when it comes onto the pitch it is fierce, it is brutal.
"I remember us going down in 2000 and we played the first Test and then we couldn't train until the Thursday because we were so physically battered by it. These guys are going to have to be mentally tough and I think the environment we have created at the moment is going to put us into good stead."
Catt was a midweek player in 1994 but a key member of the Test side in 2000, when Clive Woodward's team bounced back from losing the first Test to beating the Springboks 27-22 in Bloemfontein. That triumph was seen a giant stride towards England's 2003 Rugby World Cup triumph.
And Catt wants to see the current England generation make a similar statement three years out from hosting the next World Cup.
"It is a brilliant place to go and a very welcoming place but very, very hostile environment when you do get into the rugby circles. But there is nothing better than beating them," Catt said.
"Winning there was one of the major highlights of my career, knowing what it means to the country and to the people... I have seen both sides of it, the disappointment of losing and then winning in Bloemfontein - the heartland of South African rugby - was something that was very, very special. Not many teams achieve that."