Ukraine's President Volodymyr Zelenskyy inspected Challenger tanks and met some of his country's troops during a visit to a British Army military base in the west of England on Wednesday.
Mr Zelenskyy was making a rare foreign trip, meeting King Charles III at Buckingham Palace after addressing the Houses of Parliament where he renewed his appeal to be given fighter jets, saying his country needed “wings for freedom”.
UK Prime Minister Rishi Sunak has asked Defence Secretary Ben Wallace to investigate what jets the UK could give to Ukraine and indicated that Ukrainian pilots would be trained to use them as part of a long-term strategy.
Mr Zelenskyy repeated his pleas for fighter planes as he visited Ukrainian troops receiving training in tank warfare.
“We know that our enemy has thousands of units of armoured vehicles back from the Soviet Union heritage.," he said.
"And of course, Nato armoured vehicles are the best and yet there are only a few of them.
“When you only have 10 Nato armoured vehicles against 1,000 Soviet armoured vehicles, well what are the chances?
“We have no way out, we have to stand firm. We need armoured vehicles, we need tanks, we need fighter jets, and obviously we spend a lot of time talking about this together.”
Mr Sunak indicated that supplying fighter jets to Ukraine would involve conversations with allies that help to provide the aircraft.
“Those are conversations that the president and I are having and making sure we understand all the supply chain needs that go alongside aircraft like that — making sure they can be used and used safely, kept safely," he said.
"So we are having that conversation.
“For aircraft, that is something we are also involved in because, as I said, we have other allies involved in the provision of those bits of equipment.”
On Wednesday, the UK and Ukraine signed the London Declaration, a British-Ukrainian unity pledge that condemns the “attack on Europe’s security and the rights of people to determine their own future”.
“Our countries stand side by side in the face of this aggression. We are the closest of friends, and the most committed of partners," the pledge said.
"Inspired by the heroism and resilience of the Ukrainian people, we have come together as never before. We share a common purpose."
Thousands of soldiers from the Ukrainian Armed Forces are stationed in the West of England where they are being trained to use advanced weaponry, including the Challenger 2 tank.
In January, Mr Wallace announced that a squadron of the Challenger 2 tanks would be sent to help Ukrainian forces.
The UK was the first country to promise modern Nato tanks for Ukraine, with Germany and the US now also committed to supplying Mr Zelenskyy’s forces with dozens of vehicles.
Kyiv hopes deliveries of advanced western weaponry will break the deadlock in the conflict, nearly one year on.
The Challenger tanks are the most advanced modern tank at Ukraine’s disposal and are expected to arrive there at the end of March.
The British Army has previously sent heavily armoured tanks during operations in Bosnia and Herzegovina, Kosovo and Iraq, without losing a piece of equipment.
Built in the UK by BAE Systems and Land Armaments, the Challenger 2 is used by four armoured regiments in south-west England, at Tidworth in Wiltshire, and Bovington in Dorset.
The regiments are the Queen’s Royal Hussars, the King’s Royal Hussars, the Royal Tank Regiment, and the Royal Wessex Yeomanry, which is the reserve regiment.
Each regiment operates 56 Challenger 2 tanks and a similar number of supporting vehicles, in tasks such as reconnaissance and ammunition supply.
In 1991, a Challenger 1 ― a less armoured version of the modern Challenger 2 ― destroyed an Iraqi tank at a range of at least 4,700 metres, which is still thought to be the longest-range tank kill in history.
“One would expect a Challenger 2 to be able to take two or three direct hits from a T-72 or T-80 and still carry on, and the armour, which is highly classified, is designed to do that,” Col Hamish De Bretton-Gordon, who commanded Challenger 1 tanks during the first Gulf War, and later Challenger 2s in peacetime.