Men who wear shoes without socks and women sporting bikinis will be refused entry to parts of Lord's cricket ground.
The letter lists items of clothing that can and cannot be worn in the Lord's Pavilion, as well as the Members' Friends' Enclosures.
It warns: “Members and their guests are expected to maintain an acceptable standard of dress while in the Members’ Friends’ Enclosures.
“To avoid any embarrassment... members must ensure that their attire, and that of their guests, is appropriate.
“The minimum standard to enter the Members’ Friends’ Enclosures is ‘smart casual’ for both sexes.
“Jackets are not required, but gentlemen must wear collared shirts at all times in the stands.
“Shorts and trousers must be tailored, although denim is acceptable.”
For men, banned items include shirts that do not have a collar; T-shirts; "torn, ripped or unclean clothing"; football shorts or shorts worn for playing sport; tracksuits; garments in military camouflage colours; beachwear; and flip-flops.
For women, first allowed in the Pavilion in 1999, the list includes bikini tops and tops and dresses showing bare midriff; leggings or jodhpur-style trousers; fleeces and body-warmers; and strapless tops or dresses (unless worn under a cardigan or jacket).
Included in the letter are photographs marked with red crosses depicting what cannot be worn, among which is an image of a man in brogues whose trousers have been hitched to reveal a bare ankle.