Britain's Prime Minister Theresa May (C) walks with Liz Sweet (L) of the Commonwealth War Graves Commission, and Belgium's Prime Minister Charles Michel at the St Symphorien Military Cemetery in Mons, Belgium, on November 9, 2018, where she placed wreaths at the graves of John Parr, the first British soldier to be killed in during the First World War in 1914, and George Ellison, the last British soldier to be killed before Armistice in 1918. - British Prime Minister Theresa May and French President Emmanuel Macron are set to commemorate their countries' shared sacrifice in the First World War on Friday and discuss the future of their post-Brexit relationship. The commemoration, just ahead of the 100th anniversary of the end of WWI, will be held at the Thiepval Memorial to the Missing of the Somme, in northern France, near the Belgian border. (Photo by Gareth Fuller / POOL / AFP)

Britain's Prime Minister Theresa May (C) walks with Liz Sweet (L) of the Commonwealth War Graves Commission, and Belgium's Prime Minister Charles Michel at the St Symphorien Military Cemetery in Mons, Belgium, on November 9, 2018, where she placed wreaths at the graves of John Parr, the first British soldier to be killed in during the First World War in 1914, and George Ellison, the last British soldier to be killed before Armistice in 1918. - British Prime Minister Theresa May and French President Emmanuel Macron are set to commemorate their countries' shared sacrifice in the First World War on Friday and discuss the future of their post-Brexit relationship. The commemoration, just ahead of the 100th anniversary of the end of WWI, will be held at the Thiepval Memorial to the Missing of the Somme, in northern France, near the Belgian border. (Photo by Gareth Fuller / POOL / AFP)

Britain's Prime Minister Theresa May (C) walks with Liz Sweet (L) of the Commonwealth War Graves Commission, and Belgium's Prime Minister Charles Michel at the St Symphorien Military Cemetery in Mons, Belgium, on November 9, 2018, where she placed wreaths at the graves of John Parr, the first British soldier to be killed in during the First World War in 1914, and George Ellison, the last British soldier to be killed before Armistice in 1918. - British Prime Minister Theresa May and French President Emmanuel Macron are set to commemorate their countries' shared sacrifice in the First World War on Friday and discuss the future of their post-Brexit relationship. The commemoration, just ahead of the 100th anniversary of the end of WWI, will be held at the Thiepval Memorial to the Missing of the Somme, in northern France, near the Belgian border. (Photo by Gareth Fuller / POOL / AFP)

Britain's Prime Minister Theresa May (L) walks with Liz Sweet (L) of the Commonwealth War Graves Commission, at the St Symphorien Military Cemetery in Mons, Belgium, on November 9, 2018, where she placed wreaths at the graves of John Parr, the first British soldier to be killed in during the First World War in 1914, and George Ellison, the last British soldier to be killed before Armistice in 1918. - British Prime Minister Theresa May and French President Emmanuel Macron are set to commemorate their countries' shared sacrifice in the First World War on Friday and discuss the future of their post-Brexit relationship. The commemoration, just ahead of the 100th anniversary of the end of WWI, will be held at the Thiepval Memorial to the Missing of the Somme, in northern France, near the Belgian border. (Photo by Gareth Fuller / POOL / AFP)

A picture taken in Thiepval, northern France, on November 9, 2018 shows a view of the Thiepval Commonwealth Memorial. - The memorial commemorates more than 72,000 men of British and South African forces who died in the Somme sector before 20 March 1918 and have no known grave, the majority of whom died during the Somme offensive of 1916. (Photo by Francois Mori / POOL / AFP)

A picture taken in Thiepval, northern France, on November 9, 2018 shows a view of the Thiepval Commonwealth Memorial. - The memorial commemorates more than 72,000 men of British and South African forces who died in the Somme sector before 20 March 1918 and have no known grave, the majority of whom died during the Somme offensive of 1916. (Photo by Francois Mori / POOL / AFP)

A picture taken in Thiepval, northern France, on November 9, 2018 shows a message on a grave of the Thiepval Commonwealth Memorial. - The memorial commemorates more than 72,000 men of British and South African forces who died in the Somme sector before 20 March 1918 and have no known grave, the majority of whom died during the Somme offensive of 1916. (Photo by Francois Mori / POOL / AFP)

A picture taken in Thiepval, northern France, on November 9, 2018 shows the graves of the Thiepval Commonwealth Memorial. - The memorial commemorates more than 72,000 men of British and South African forces who died in the Somme sector before 20 March 1918 and have no known grave, the majority of whom died during the Somme offensive of 1916. (Photo by Francois Mori / POOL / AFP)

British Prime Minister Theresa May (L) and French President Emmanuel Macron visit the Thiepval Memorial, northern France, on November 9, 2018. - Thiepval Commonwealth Memorial commemorates more than 72,000 men of British and South African forces who died in the Somme sector before 20 March 1918 and have no known grave, the majority of whom died during the Somme offensive of 1916. (Photo by Francois Mori / POOL / AFP)

This general view shows the Thiepval Commonwealth Memorial, in Thiepval, northern France on November 9, 2018. - The memorial commemorates more than 72,000 men of British and South African forces who died in the Somme sector before March 20, 1918 and have no known grave, the majority of whom died during the Somme offensive of 1916. (Photo by Francois Mori / POOL / AFP)

Before completion, British artist Rob Heard poses for photographs in front of rows of what will be 72,396 shrouded figures forming his piece of commemorative art 'Shrouds of the Somme' to mark the upcoming centenary of the end of World War I, in the Queen Elizabeth Olympic Park, London, Wednesday, Nov. 7, 2018. Each figure is a human form, individually shaped, shrouded and made with a name of the 72,396 missing British and Commonwealth servicemen who were killed fighting in the Somme area of France between July 1, 2016 and March 20, 1918 who have no known grave and whose names are engraved on the Thiepval Memorial in France. World War I ended on November 11, 1918. (AP Photo/Matt Dunham)

Members of the British military's 1st Battalion The Royal Anglian Regiment, The Vikings, help layout out in rows what upon completion will be 72,396 shrouded figures forming British artist Rob Heard's piece of commemorative art 'Shrouds of the Somme' to mark the upcoming centenary of the end of World War I, in the Queen Elizabeth Olympic Park, London, Wednesday, Nov. 7, 2018. Each figure is a human form, individually shaped, shrouded and made with a name of the 72,396 missing British and Commonwealth servicemen who were killed fighting in the Somme area of France between July 1, 2016 and March 20, 1918 who have no known grave and whose names are engraved on the Thiepval Memorial in France. World War I ended on November 11, 1918. (AP Photo/Matt Dunham)

British artist Rob Heard's piece of commemorative art 'Shrouds of the Somme' consisting of 72,396 shrouded figures is displayed after its completion to mark the upcoming centenary of the end of World War I, in the Queen Elizabeth Olympic Park, London, Wednesday, Nov. 7, 2018. Each figure is a human form, individually shaped, shrouded and made to a name of the 72,396 missing British and Commonwealth servicemen who were killed fighting in the Somme area of France between July 1, 2016 and March 20, 1918 who have no known grave and whose names are engraved on the Thiepval Memorial in France. World War I ended on November 11, 1918. (AP Photo/Matt Dunham)

After completion, a member of the British military's 1st Battalion The Royal Anglian Regiment, The Vikings, lays an additional shrouded figure representing all the casualties of World War I, alongside 72,396 shrouded figures forming British artist Rob Heard's piece of commemorative art 'Shrouds of the Somme' to mark the upcoming centenary of the end of World War I, in the Queen Elizabeth Olympic Park, London, Wednesday, Nov. 7, 2018. Each figure is a human form, individually shaped, shrouded and made to a name of the 72,396 missing British and Commonwealth servicemen who were killed fighting in the Somme area of France between July 1, 2016 and March 20, 1918 who have no known grave and whose names are engraved on the Thiepval Memorial in France. World War I ended on November 11, 1918. (AP Photo/Matt Dunham)

Shrouded figures forming part of British artist Rob Heard's piece of commemorative art 'Shrouds of the Somme' consisting of 72,396 shrouded figures is displayed after its completion to mark the upcoming centenary of the end of World War I, in the Queen Elizabeth Olympic Park, London, Wednesday, Nov. 7, 2018. Each figure is a human form, individually shaped, shrouded and made to a name of the 72,396 missing British and Commonwealth servicemen who were killed fighting in the Somme area of France between July 1, 2016 and March 20, 1918 who have no known grave and whose names are engraved on the Thiepval Memorial in France. World War I ended on November 11, 1918. (AP Photo/Matt Dunham)

Shrouded figures forming part of British artist Rob Heard's piece of commemorative art 'Shrouds of the Somme' consisting of 72,396 shrouded figures are displayed after its completion to mark the upcoming centenary of the end of World War I, in the Queen Elizabeth Olympic Park, London, Wednesday, Nov. 7, 2018. Each figure is a human form, individually shaped, shrouded and made to a name of the 72,396 missing British and Commonwealth servicemen who were killed fighting in the Somme area of France between July 1, 2016 and March 20, 1918 who have no known grave and whose names are engraved on the Thiepval Memorial in France. World War I ended on November 11, 1918. (AP Photo/Matt Dunham)

Shrouded figures forming part of British artist Rob Heard's piece of commemorative art 'Shrouds of the Somme' consisting of 72,396 shrouded figures are displayed after its completion to mark the upcoming centenary of the end of World War I, in the Queen Elizabeth Olympic Park, London, Wednesday, Nov. 7, 2018. Each figure is a human form, individually shaped, shrouded and made to a name of the 72,396 missing British and Commonwealth servicemen who were killed fighting in the Somme area of France between July 1, 2016 and March 20, 1918 who have no known grave and whose names are engraved on the Thiepval Memorial in France. World War I ended on November 11, 1918. (AP Photo/Matt Dunham)