LONDON, ENGLAND - NOVEMBER 14: British Prime Minister Theresa May and her husband Philip May attend the Lord Mayor's Banquet at Guildhall on November 14, 2016 in London, England. The Lord Mayor of London, Andrew Parmley, is hosting the annual Lord Mayor's Banquet in London's Guildhall which will feature speeches from the Prime Minister and the Archbishop of Canterbury. Andrew Parmley was recently elected 689th Lord Mayor of the City of London, a role that has been in existence since 1189. (Photo by Carl Court/Getty Images)

LONDON, ENGLAND - NOVEMBER 14:  British Prime Minister Theresa May and her husband Philip May attend the Lord Mayor's Banquet at Guildhall on November 14, 2016 in London, England. The Lord Mayor of London, Andrew Parmley, is hosting the annual Lord Mayor's Banquet in London's Guildhall which will feature speeches from the Prime Minister and the Archbishop of Canterbury. Andrew Parmley was recently elected 689th Lord Mayor of the City of London, a role that has been in existence since 1189.  (Photo by Carl Court/Getty Images)

LONDON, ENGLAND - NOVEMBER 14: British Prime Minister Theresa May (R) is accompanied by the Lord Mayor of London, Andrew Parmley as she attends the Lord Mayor's Banquet at Guildhall on November 14, 2016 in London, England. The Lord Mayor of London, Andrew Parmley, is hosting the annual Lord Mayor's Banquet in London's Guildhall which will feature speeches from the Prime Minister and the Archbishop of Canterbury. Andrew Parmley was recently elected 689th Lord Mayor of the City of London, a role that has been in existence since 1189. (Photo by Carl Court/Getty Images)

LONDON, ENGLAND - NOVEMBER 14: British Prime Minister Theresa May (R) is accompanied by the Lord Mayor of London, Andrew Parmley as she attends the Lord Mayor's Banquet at Guildhall on November 14, 2016 in London, England. The Lord Mayor of London, Andrew Parmley, is hosting the annual Lord Mayor's Banquet in London's Guildhall which will feature speeches from the Prime Minister and the Archbishop of Canterbury. Andrew Parmley was recently elected 689th Lord Mayor of the City of London, a role that has been in existence since 1189. (Photo by Carl Court/Getty Images)

LONDON, ENGLAND - NOVEMBER 14: British Prime Minister Theresa May and her husband Philip May attend the Lord Mayor's Banquet at Guildhall on November 14, 2016 in London, England. The Lord Mayor of London, Andrew Parmley, is hosting the annual Lord Mayor's Banquet in London's Guildhall which will feature speeches from the Prime Minister and the Archbishop of Canterbury. Andrew Parmley was recently elected 689th Lord Mayor of the City of London, a role that has been in existence since 1189. (Photo by Carl Court/Getty Images)

LONDON, ENGLAND - NOVEMBER 14:  British Prime Minister Theresa May and her husband Philip May attend the Lord Mayor's Banquet at Guildhall on November 14, 2016 in London, England. The Lord Mayor of London, Andrew Parmley, is hosting the annual Lord Mayor's Banquet in London's Guildhall which will feature speeches from the Prime Minister and the Archbishop of Canterbury. Andrew Parmley was recently elected 689th Lord Mayor of the City of London, a role that has been in existence since 1189.  (Photo by Carl Court/Getty Images)