The declaration, written by Britain's Foreign Secretary Arthur Balfour during the First World War, expressed the government's support for "the establishment in Palestine of a national home for the Jewish people".
Thursday's commemoration, culminating in the dinner hosted by descendants of Balfour and of the recipient of his declaration, Jewish community leader Walter Rothschild, requires Britain to strike a delicate diplomatic balance. Labour leader Jeremy Corbyn declined an invitation to the event and is expected to send a representative in his place.
May will also hold talks with Netanyahu in Downing Street, where she hopes to make clear Britain's continuing support for the nuclear deal with Iran, despite US President Donald Trump's disavowal of the agreement last month. On Saturday, he will meet with Britain's Chief Rabbi Ephraim Mirvis before flying back to Israel later in the day.
As he left Israel on Wednesday, Netanyahu thanked the British government and said it was time for Palestinians to come to terms with the past.
Some Arab lawmakers in the Israeli parliament said they would boycott the celebrations, and protests are planned across several days in London by organisations pledging solidarity with the Palestinians. It wasn't a tragedy.
A 100 years of pain and suffering at the expense of others - more than 12 million displaced Palestinians to be exact - is not something to be celebrated. "I hope they change their mind, because if they do, they can move forward finally to making peace between our two peoples", he said.
Despite the criticism and calls for the British government to apologise for the Balfour declaration, they will instead be celebrating the "special" occasion with their Israeli counterparts.
The letter, coordinated by the Conservative Friends of Israel and published in The Daily Telegraph on Thursday, hails Israel as "one of modern history's most remarkable success stories - a thriving democracy and a high-tech power house". The UK has rejected calls to apologize for its role.
"True Promise: Palestine between Balfour Declaration and Divine Promise" is the theme of the conference. The occupation and annexation of land intended for a Palestinian state has never been recognized by the global community, and hopes for a two-state solution to the Israeli-Palestinian conflict are greatly diminishing.
He was referring to a clause in the document which said nothing should prejudice the civil and religious rights of existing non-Jewish communities.
The British Mandate expired on 14 May 1948 and the Jewish leadership in Palestine declared an independent Israeli state.