The Mansion House in London has always been associated with high level dinners often seen on TV with the Prime Minister, Chancellor or Heads of State being escorted into dinner and always wearing White Tie. There will always be a Toastmaster present to make announcements.
Other organisations such as Liveries also use the Mansion House when white tie is the dress code. The white tie outfit is a black evening tailcoat with Marcella accessories, being waistcoat, shirt and bow tie. The Marcella waistcoat is always starched from very stiff to less so and has removable buttons, often referred to as bachelor buttons, so the front can be pressed flat. The waistcoat will always be strap-backed, which is adjustable in length so it fits exactly to the correct position under the tail coat.