This is from the Wimbledon website regarding the Royal Box. The highlighted area is mine:
The Royal Box has been used for the entertainment of friends and guests of Wimbledon since 1922. The Royal Box has 74 seats. They are dark green Lloyd Loom wicker chairs.
British and overseas Royal Families are invited as well as heads of government, people from the world of tennis, commercial partners, British armed forces, prominent media organisations, supporters of British tennis and other walks of life.
Invitations come from the Chairman of the All England Club, taking into account suggestions from members of The Championships’ Organising Committee, The Lawn Tennis Association and other relevant sources.
Guests are invited to the Clubhouse for lunch, tea and drinks at the end of the day.
Protocol - dress is smart, suits/jacket and tie, etc. Ladies are asked not to wear hats, as they tend to obscure the vision of those seated behind them.
Bowing/Curtseying on Centre Court
In 2003, in accordance with the wishes of HRH The Duke of Kent, the Club’s President, it was agreed that the time was right to discontinue the tradition of players bowing/curtseying to members of the Royal family on entering or leaving the Centre Court. The only exceptions will be for HM The Queen and HRH The Prince of Wales.
END
This is the link
Royal Box - The Championships, Wimbledon 2015 - Official Site by IBM
So you cant get in there without an invite.
By the way, Tim Henman is on the Wimbledon committee.
but I've just seen the Duchess of Gloucester watching the Federer v Raonic match 
