Jeans, flip flops and short skirts are just not tennis, Wimbledon officials have decided ahead of the championships that start tomorrow.
And just to ensure there is no confusion, they have also provided photographic guidance to hammer home their point.
All England Club, has hosted the tennis championships for almost 150 years.
According to some at the illustrious club, the guide effectively warns: "No riff-raff please, we're Wimbledon."
The members' handbook now contains five photographs of an attractive couple illustrating how to avoid the disgrace of being banned from the clubhouse, the Daily Mail reported.
They are considered to be wearing "acceptable dress" in just one picture, which appears alongside the words: "The dress standard for gentlemen is lounge suit or tailored jacket, shirt, tie, trousers and dress shoes."
"Ladies are expected to dress to a similar standard."
The other photographs illustrate "unacceptable dress". The various sartorial sins committed include "T-shirts, distressed jeans and trainers, bare midriffs, jeans and flip flops".
Strapless tops and shorts are banned, as are "zipper jackets, casual or scuffed shoes, hoodies, pumps and short skirts".
"The Club's dress standards in the Members' Enclosure will be strictly enforced. To avoid any embarrassment please ensure your attire and that of your guests is appropriate," Members are warned.
But even this may not quite be enough, as it adds: "Notwithstanding the dress standards outlined, the Club reserves the right to refuse entry to any person considered unsuitably dressed."
The new guidance appears in the latest issue of the All England Club's members' booklet, being sent out in time for the tennis championships.
It comes just days after the 225-year-old Marylebone Cricket Club issued its first pictorial dress guidelines for visitors to Lord's cricket ground in north London.
Organisers at Royal Ascot also tightened the dress code and deployed fashion police to ensure racegoers complied.
A member of the All England Club said: "One or two of the members have nicknamed these photos "No chavs please, we're Wimbledon".