The Nato flag will fly above Downing Street today as the alliance marks 73 years since its foundation.
The banner will also be raised in places where the UK has contributed Nato troops, from the HMS Prince of Wales aircraft carrier in the north, to Estonia in the east and RAF patrols in Romania in the south.
Nato has sent troops, ships and aircraft to countries and the region near Ukraine to strengthen deterrence in the war. As the leading European contributor to Nato, the UK has been at the forefront of this action.
The UK has directly supplied 6,000 missiles, 4,000 anti-tank weapons and anti-aircraft projectiles to bolster Ukrainian defences.
Last week the Defence Secretary Ben Wallace hosted a meeting of 30 countries from across Nato and beyond to co-ordinate future military aid to Ukraine.
This week, British Prime Minister Boris Johnson will welcome Polish President Andrzej Duda and German Chancellor Olaf Scholz to discuss the tough and decisive response from allies to the situation in Ukraine.
“Seventy-three years ago today, the founding members of Nato came together, united loosely by geography but bound more tightly by a shared belief in freedom and sovereignty," Mr Johnson said.
"Three quarters of a century later that conviction and drive endures.
“It is that self-same freedom which the people of Ukraine are fighting for with every fibre of their being.
“As members of the greatest security alliance in the history of the world, we have a responsibility to give them everything they need to face down this barbaric attempt to subjugate the Ukrainian people.
“As the largest European contributor to the alliance and as a staunch friend to Ukraine, the UK will continue to do just that.”
As part of the Nato response to Russian President Vladimir Putin’s actions, the UK has doubled its troop presence in Estonia, sent the HMS Trent and HMS Diamond to the Eastern Mediterranean and sent Royal Air Force Typhoons to patrol the skies of Romania and Poland.
HMS Trent is conducting Nato exercises with Merlin Helicopters and RAF P8 Poseidon Maritime Patrol Aircraft.
They will be shortly joined by HMS Diamond, a Type 45 destroyer, which set sail from Portsmouth on Sunday.
On Monday, the government also announced that one of Mr Johnson’s top foreign policy advisers will be the UK’s next permanent representative to Nato.
David Quarrey, who was previously the deputy national security adviser, will help to advance the response to the unfolding crisis in Ukraine and the future of the alliance.
He will take over from Dame Sarah MacIntosh this month. Mr Johnson approved the appointment of Mr Quarrey on the recommendation of Foreign Secretary Liz Truss.
The Foreign, Commonwealth and Development Office said Mr Quarrey was one of the UK’s most experienced senior diplomats.
He has been UK ambassador to Israel, director for the Middle East and North Africa at the Foreign Office, and director for foreign policy in the National Security Secretariat of the Cabinet Office.
Mr Quarrey held postings in India and Zimbabwe, and at the UK’s permanent representation to the UN in New York.
“I am honoured to take up the position of UK permanent representative to Nato,” Mr Quarrey said.
“I look forward to leading the excellent joint FCDO and MoD [Ministry of Defence] team as we work with our allies to keep our country and citizens safe.”
Ms Truss said: “Nato is vital for European and global security. We will work to strengthen the alliance in the face of Russian aggression.
“I am pleased to appoint David, who is an experienced diplomat and will lead the UK’s efforts working with our Nato allies.
“I congratulate him on his appointment.”
Ms MacIntosh will be transferred to another diplomatic service appointment.