For many centuries Royal Weddings were private events that took place in Palaces and Castles like Windsor. In George V´s reign everything changed. He wanted his children to marry in Westminster Abbey publicly so that the working people could take part in it.
Those were hard and precarious times for monarchies all over Europe ( in 1910 king Manuel II of Portugal had to live in exile after the implantation of the republic and in Russia the Czar was overthrown with the Russian revolution). King George V was determined that the same would not happen in Britain, so he wanted to open up the monarchy.
When his son (later king George VI) married the Scottish aristocrat Lady Elizabeth Bowes-Lyon, in 1923 the wedding captivated the nation and became a national event.
The wedding of Princess Elizabeth (later Queen Elizabeth II) and the Duke of Edinburgh took place in 1947, in Westminster Abbey.
The Wedding of Prince Charles (the heir to the throne) and Lady Diana Spencer took place in St. Paul´s Cathedral in 1981. ( The Abbey could not fit in the 2660 guests and dignitaries invited )
Prince Charles married Camilla Parker Bowles at Windsor in 2005
The Wedding of Prince William and Catherine Middleton in 2011