The British in January pledged 14 main battle tanks to help Ukraine defend itself, denying a Ukrainian suggestion that more are already approved.
Leopard 2 and Challenger 2 Steal a March on the Abrams in Ukraine – Defense Security Monitor
Ukrainian resources report the appearance of British Challenger 2 tanks in the south direction
The Challenger 2 Tank Already Has a Lot of Armor. The Ukrainians Added More.
Is there a good reason for not buying a Challenger tank? - Quora
How and when will the tanks promised to Ukraine be delivered?
UK will give Ukraine twice as many Challenger 2 tanks as originally promised
Are More Ex-British Challenger 2 Tanks Bound For Ukraine?
Poland confirms T-72 tank delivery to Ukraine, with Challenger 2 tanks to fill gap
What are we doing in Ukraine? – Georgetown Security Studies Review