Prime Minister Rishi Sunak has met Benjamin Netanyahu at Downing Street as the Israeli leader faces domestic turmoil over judicial reforms.
Mr Sunak greeted Mr Netanyahu outside No 10 before talks over security and the threat from Iran.
Mr Netanyahu will also meet Home Secretary Suella Braverman on his one-day visit.
Hundreds of protesters gathered at the gates of Downing Street to demonstrate against the Israeli PM's policies.
There was a cacophony, including shouts of "shame" and "traitor", as Mr Netanyahu made the short walk from his convoy to the steps of Number 10.
A planned photo opportunity for media at the start of the talks was cancelled, and there was no joint statement.
The visit comes at a time of political turmoil in Israel, with the country gripped by months of some of the biggest demonstrations in its history.
Mr Netanyahu has defied calls to scrap a shake-up of the legal system, amid warnings the crisis is not only causing social upheaval but could harm Israel's security.
Growing numbers of military reservists are refusing to serve in protest.
Thursday saw tens of thousands of Israelis take to the streets across the country, in scenes which have been repeated weekly and escalated since the start of the year.
Downing Street said that in his meeting with Mr Netanyahu, Mr Sunak "stressed the importance of upholding the democratic values that underpin our relationship, including in the proposed judicial reforms in Israel".
It said the two men also discussed the war in Ukraine and Iran's "destabilising activity", as well as its nuclear programme. It said the leaders welcomed an agreement signed this week aimed at deepening technical, trade and security ties between the UK and Israel.
Although previous visits to the UK by Mr Netanyahu have been met with demonstrations by pro-Palestinian groups, Friday's protests - led by British and Israeli Jews, with many waving Israeli flags - were an unusual sight.
On the opposite side of the road, hundreds of protesters from the Palestine Solidarity Campaign held a demonstration against Mr Netanyahu's visit and the State of Israel, while a third, small rally was also held nearby by supporters of Mr Netanyahu.
Opponents of the Israeli prime minster say he is using the judicial reforms, which will weaken the power of the Supreme Court among other things, to bolster himself and shield policies of his government - the most right-wing in Israel's history.
Mr Netanyahu has accused critics of disrespecting voters who gave his coalition and its reform platform a commanding win in November's elections.