Ukrainian President Volodymyr Zelenskiy arrived in London on Wednesday to seek more military deliveries from the United Kingdom.
He will meet Prime Minister Rishi Sunak and King Charles and address parliament.
Britain has trained 10,000 Ukrainian troops brought to battle readiness in the last six months and will train a further 20,000 soldiers this year.
Ukraine's allies have promised hundreds of tanks and armoured vehicles to help Kyiv resist the Russian assault.
Zelenskiy will travel to Brussels tomorrow to attend the European Union summit.