The South Africa-born centre will be 36 three days after England's pivotal World Cup pool clash against the Springboks in Paris on September 14.
Only two England players - prop Paul Rendall and hooker Dorian West - were older than Catt when starting a World Cup tournament.
His longevity - Catt's Test debut more than 13 years ago came in the same England side as Will Carling, Rory Underwood, Rob Andrew, Brian Moore and Dean Richards - is testament to an iron-willed determination that keeps him at the peak of his physical and mental powers.
He will become the ninth red rose player to win 70 caps when he skippers England against World Cup warm-up opponents France at Twickenham on Saturday.
And although Catt is not taking World Cup selection for granted, a place in head coach Brian Ashton's 30-man squad looks certain.
It would be his fourth World Cup campaign - equalling Jason Leonard's England record - and the former Bath star, by his own admission, is "buzzing."
He said: "I probably wouldn't haven't thought I would be in this World Cup - I am not there yet, either - but since my move to London Irish and (rugby director) Brian Smith coming on board, the way we've played at Irish has definitely rejuvenated me.
"Mentally, I have been absolutely buzzing. I would like to think I have played consistently for Irish for the past two years.
"I have always said I don't particularly want to give up international rugby until I give up club rugby. I have always wanted to strive to be the best in my position in the country.
"Fortunately, my body has held out. I still have a massive drive to be successful and to work exceptionally hard."