Thank goodness Alexander1917!
As to Robert's comments about Royal Dukedoms being superfluous! I tend to agree with this opinion as of the present climate in the UK! In previous ages, a Prince was generally given a Dukedom upon reaching his majority, as a tacit sign from the reigning monarch, that the former was of an age to start taking an active and responsible role in governance! Especially when large territories where attached to said Duchies! Later with the general dissolution of territorial Duchies, brought about most significantly after the Wars of the Roses, which did much to reveal the faults of granting territorials to collateral branches of the dynasty, Duchies were replaced as we have seen over time with 'landless' Dukedoms.
Queen Victoria for example tended to delay giving out Dukedoms. The Dukedom of Albany was the last created for a younger son of a monarch not in 'direct' line to the throne, but whose male line post grandson descendants 'were' still going to hold the status of Prince/Princess and 'Highness', which was only limited by George V in 1917. Thereafter the status of Prince/Princess and Royal Highness ended with male line grandchildren and the status of Highness became obsolete altogether.
In 1917, I tend to think that the idea of Royal Dukedoms was regarded as a way of giving the senior male line descendants of the younger sons of monarchs, a suitable social rank for generations to come. This was subsequently born out in the grandchildren of Harry Gloucester and George Kent. As Albert Windsor is the first legitimate lineal male line descendant of George V not to have any title, this situation of 'commoner' members of the extended Windsor family will in time become a norm!
I also wonder, that the decision to recreate the Dukedom of Edinburgh is not perhaps, fueled by a desire to continue it as a separate entity from the crown, and ensure its continuation in order to maintain its links to the Duke of Edinburgh Awards Scheme, in which Edward Wessex is now a principal player. This would, perhaps prove a fitting and satisfactory legacy to leave for the present Duke, who will go upstairs knowing that his youngest son and grandson will in due course carry on his personal charitable projects not only in person but in name too!