Invitations are out

The invitations to the Royal wedding have been sent out ... I don't expect an invite ... and, yes, invite is a noun, as well as a verb, at least according to the Oxford English Dictionary, the doyen of dictionaries.

Invite is a noun,  "The act of inviting, an invitation."  The use of the word "invite" as a noun is found as far back as 1659 "Bishop Cranmer gives him an earnest invite to England."   In 1818,  from Lady Morgan's Passages from My Autobiography, "For Monday we have had three dinner invites." 

Invite is also a verb.  I do not expect to be invited to William's wedding.  I did receive an invite to join friends for dinner.

It is being reported that 40 foreign royals have been invited.  Buckingham Palace has never released a complete list of guests for royal weddings.  I covered The Duke of York's wedding for the Associated Press. and received a press kit with all of the appropriate information.  One of the press releases was the list of the members of the reigning royal houses, but not other royals, including the family members.   On the day of Prince Edward's wedding, the palace did release a list of royals that included some of the family members.  But the palace has never been good at releasing a complete list of guests, including foreign royals, distant cousins, and others.

One assumes that invitations have been sent all of the reigning royal houses.   The invitations are sent in the name of the Queen, not the Prince of Wales nor the bride and groom, which makes me think that the royal delegations will be of the highest level, i.e, sovereigns and consorts, but not their heirs.  Six hundred of the wedding guests will be invited to the wedding breakfast reception after the ceremony.   This reception is hosted by Queen Elizabeth II.  It seems plausible that most of the reigning monarchs will be attending.
Here is my possible list:  Queen Beatrix,  Margarethe and Henrik from Denmark,  Harald and Sonja from Norway,  Carl XVI Gustaf and Siliva of Sweden,  Juan Carlos and Sofia of Spain, Henri and Maria Teresa of Luxembourg,  Hans-Adam and Marie of Liechtenstein, Albert and Paola of the Belgians and Albert of Monaco with Miss Wittstock, although she may be seated separately as she is not a Serene Highness.   This means she will sit with Albert, but not be in the official procession.
King Juan Carlos does not usually attend royal weddings, but he and Sofia were planning to attend Charles and Diana's wedding, but had to bow out because of that little problem of Charles and Diana spending a part of their honeymoon in Gibraltar.  The Spanish couple may choose to attend simply because they were unable to be at Charles' wedding. 

Unlike other royal weddings,  foreign contingents at British royal weddings are largely limited to one or two people per family.   The Sovereign and Spouse, for example or the Heir and spouse.  Or perhaps both.  In 1981, King Olav attended Charles and Diana's wedding, and was accompanied by the Crown Prince and Crown Princess.  The Norwegians are more closely related to the British royal family, as Olav's mother was the sister of George V. Hereditary Grand Duke Henri of Luxembourg, who married earier that year, did not accompany his parents to Charles' wedding.  But the rest of the heirs to the European thrones had not yet reached their majority, so none would have been able to attend.  It is entirely possible that several of the European sovereigns will be accompanied by their spouses and their heirs and their spouses. 
Several of the sovereigns may choose to send their heir apparent and spouse to the wedding.  I am not sure when Crown Princess Mary's maternity leave ends, but if she is still on official leave on April 29,  she and Crown Prince Frederik will not be attending the wedding.  Crown Prince Haakon and Crown Princess Mette-Marit did attend the Prince of Wales' second wedding, as Haakon's parents attended the first wedding.  This leads me to think that the King and Queen will attend William's wedding.
It would be out of character to include the Sovereigns and the heirs at a British royal wedding, but it is possible.  Princess Grace was accompanied by her son, the then Hereditary Prince Albert.

Grand Duke Henri's appearance may depend on his health.   Maria Teresa could be accompanied by her son, Hereditary Grand Duke Guillaume.

Expect to see King Constantine II and Queen Anne Marie to attend, along with all or most of their five children (and spouses.)  Crown Princess Margarita and Prince Radu of Romania will be attending as will Crown Prince Alexander and Crown Princess Katherine of Serbia and King Simeon and Queen Margarita of Bulgaria.
You can add to the mix a selection of Hesses, Hohenlohe-Langenburgs, and Badens, including Princess Margarita of Baden, who is the Duke of Edinburgh's niece.

The Crown Prince of Japan will probably represent his father, the Emperor.  Press reports have stated that he will be accompanied by the Crown Princess, but nothing has been confirmed.   The King of Thailand is unwell, and may send a rep.  He sent his daughter to Charles and Diana's wedding.
The Sultan of Brunei is probably on the guest list.  He brought both wives to Prince Edward's wedding.  The Sultan divorced his second wife in 2003.  He remarried, and divorced the third wife last year.  At this time, the Sultan has only one wife.

What about the Kings of Lesotho and Swaziland?  They are possible guests, as is the very, very rich Aga Khan.

Everything is pure speculation.  We won't know who is coming until April 29, unless a guest comes out publicly, and states that they have been invited.