Kate Middleton makes emotional visit to London's Imperial War Museum

In what was a more sombre royal engagement ahead of Armistice Day, Catherine, the Duchess of Cambridge has viewed letters relating to her great-grandmother's three brothers who all died during WWI.

Catherine made an emotional and solo visit to London's Imperial War Museum on Wednesday to pay her respects to those who had fallen during the war, but also to her family.

The glamorous Duchess wore a royal blue, long-sleeved dress by Jenny Peckham with nude, suede heels.

Her elegant outfit was paired with a simple nude clutch, silver watch, and her signature blow-dried wave.

Her family's letters, which form part of the museum's documents archive, have provided both an insightful yet poignant account of soldiers' time spent in the trenches.

The Duchess of Cambridge's great-uncles, Francis, Maurice and Lionel Lupton, were all killed in action during WWI. Photo / Getty Images

The Duchess was shown several of the documents including a letter of condolence to her family from the Keeper of the Privy Purse at Buckingham Palace.

Catherine's great-great-grandfather, Francis Martineau Lupton, had five children including three sons Francis, Maurice and Lionel who were all killed in action.

Their sister Olive, who was as a nurse in the Voluntary Aid Detachment, is the Duchess' great-grandmother.

Catherine, Duchess of Cambridge views the letters relating to her great-uncles. Photo / Getty Images

Major Francis Lupton, who was the eldest, served with the 8th Battalion West Yorkshire Regiment and was killed by a bomb on February 19, 1917.

Lieutenant Lionel Lupton, the youngest of the three, had been killed in action a year earlier after serving with the 28th Brigade Royal Field Artillery.

Captain Maurice Lupton served with the 7th Battalion West Yorkshire Regiment and also spent time in the trenches.

He was the first of the brothers to be killed during the war in 1915.

A cascade of poppies adorns the facade of London's Imperial War Museum. Photo / Getty Images

Catherine also toured the First World War Galleries and met with historians, curators and a fellow descendant of a WWI soldier.

Her visit to the museum is her second official royal engagement this week after she attended the Coach Core Essex programme in Basildon with Prince William on Tuesday.