The Duke and Duchess of Cambridge are celebrating four years of marriage after the spectacular royal wedding on April 29, 2011.

William and Kate are obviously busy with royal baby stuff so while we wait for the next photo of them, which will inevitably be alongside their second child, here are 12 pictures showing their story so far.

After meeting at the University of St Andrews in 2001, Kate Middleton and Prince William were photographed separately as they left their graduation ceremony on June 23, 2005.

However ahead of the royal wedding in 2011, the Middleton family released this photo of them celebrating after the ceremony.

Kate and William in 2005
Kate and Wills in 2005 (The Middleton Family/AP)

Kate and William were photographed together during university and she attended his 21st birthday party at Windsor Castle in June 2003, however it was not until March 2004 that their romance was exposed.

The pair were pictured kissing for the first time in 2006 and they were photographed at the Six Nations rugby tournament in February 2007.

Harry, William and Kate watching the Six Nations rugby in 2007
Harry, William and Kate watching the Six Nations rugby in 2007 (Alastair Grant/AP)

However in April 2007, they broke up. A photo taken at a memorial concert for Princess Diana at Wembley showed them sitting apart in June 2007.

Britain's Prince William (left, front row) sits a little distance away from his former girlfriend Kate Middleton (second left, back row) at Wembley Stadium, north-west London, during today's star-studded pop concert in memory of Diana, Princess of Wales.
Prince William and Kate Middleton sitting apart at a memorial concert for Princess Diana (Stephen Hird/PA)

It was only a few months before the couple rekindled their romance and this photo taken at RAF Cranwell when Prince William received his RAF Wings shows them looking happier than ever.

Britain's Prince William and his then girlfriend Kate Middleton walking together at RAF Cranwell, England (Michael Dunlea/AP)
Prince William and Kate Middleton walking together at RAF Cranwell, England (Michael Dunlea/AP)

And the news every royal fan had been waiting for came in November 2010 when Prince William popped the question.

Royal engagement
The royal couple at a photocall to celebrate their engagement in 2010 (John Stillwell/PA)

The royal wedding took place in April 2011.

Royal wedding 2011
Royal wedding (David Jones/PA)

And one of their many royal tours was the Diamond Jubilee tour of the Far East in 2012.

Diamond Jubilee tour 2012
Diamond Jubilee tour 2012 (Chris Jackson/PA)

In December, Kate’s pregnancy was revealed early when she was admitted to hospital with acute morning sickness.

Duke and Duchess of Cambridge pregnancy
Acute morning sickness gave the game away (Andrew Matthews/PA)

And Prince George arrived in July 2013.

Duke and Duchess of Cambridge with Prince George
Welcome Prince George (Dominic Lipinski/PA)

When they went on tour Down Under to Australia and New Zealand in 2014, Prince George, now a toddler, was in tow.

Duke and Duchess of Cambridge with Prince George
A right royal tour (PA)

But they left him at home when they went to US in December last year after announcing in September that Kate was pregnant with their second child.

Duchess of Cambridge, Duke Prince William
It’s rude to point! (Frank Franklin II/AP)

And here is one of the last pictures of the Duchess and Duke together before she went on maternity leave.

Duke and Duchess of Cambridge
Doesn’t look like it’s going to fit. (Ian Vogler/Daily Mirror/PA)

The next time Kate and William are seen together, another tiny royal is likely to be in the photo.