The visit of Ukrainian President Volodymyr Zelensky to the UK is designed to shore up support ahead of an expected Russian offensive.
Mr Zelensky has said repeatedly that the coming months will see a turning point in the conflict.
He made a virtual address to the parliament from Kyiv just under a year ago.
It is only Mr Zelenksy's third visit abroad since the Russian invasion after stopping off in Poland last December on a visit to Washington.
Like the visit to the UK, these visits were not announced in advance for obvious security reasons.
The aim of the trips is the same: To encourage Western allies to step up military support.
When he addressed the US Congress he compared Ukraine's war with the battles fought by American troops against Hitler's army in 1944.
He also warned that the war in Ukraine cannot be ignored and said it affects the rest of the world.
"The world is too interconnected and interdependent to allow someone to stay aside and at the same time to feel safe when such a battle continues," he said.
In the UK, the public seems to broadly support that view.
According to recent surveys, 63% support supplying Ukraine with fighter jets and 64% support giving tanks.
As the recent reluctance by Germany to supply tanks shows, Western leaders are wary of escalating the conflict.
However, Britain was one of the first countries to offer military support and Mr Zelensky has repeatedly acknowledged that this came at a crucial time.
The British government has recently announced that British training of Ukrainian forces will be expanded to cover fighter jet pilots and marines.
This will be combined with fresh sanctions against Russia.
The UK has already announced plans to send Challenger 2 tanks and to train Ukrainian troops in their use.
The biggest stumbling block has been long-range missiles which could be used against Russia itself.
Britain has regarded this as a step too far.
However, a No 10 spokesperson has said Ukraine will be offered "longer range capabilities".
The aim is still defensive and is to disrupt Russia's ability to target Ukraine's critical national infrastructure.
Even though the British public is in favour of military support for Ukraine that does not mean they are not concerned about the consequences.
A YouGov tracker poll reports that 71% of Britons believe that a major world conflict is very or somewhat likely within the next 20 years.