I was still hundreds of metres from the Royal Albert Hall when I spotted the first Ukrainian flag. It was the first of many worn as capes, not to mention the badges, hats and colour-coordinated outfits scattered around the near-capacity auditorium. If this sounds reminiscent of the annual flag-fest on the Last Night of the Proms, think again: this crowd was sombre, even subdued. But that changed as members of the Ukrainian Freedom Orchestra started to filter on to the stage, met by a battery of applause and an immediate standing ovation. It was an impressive start for an ensemble that didn’t exist a fortnight ago, rapidly assembled from professional Ukrainian musicians in Ukraine and across Europe. One musician I spoke to – a trombonist with the Kyiv National Opera – had travelled straight from Lviv to Warsaw for the orchestra’s first rehearsal under founding conductor Keri-Lynn Wilson. Instantly recognisable in his concert dress outside RAH, he told me this was his first trip to London: “Like a dream come true”. There were first-time prommers, too. A Ukrainian and her young daughter, dressed in matching embroidered white shirts, had recently come to London under the Homes for Ukraine programme. “We want to support Ukrainian musicians and music,” she explained. “It’s a very big event for us – very emotional. It’s a possibility to support Ukraine on all levels.” Meanwhile the two young Ukrainian refugees sitting next to me were taking carefully posed selfies. “This is a fantastic building!” one beamed. No wonder the hush that fell for the start of Ukrainian composer Valentin Silvestrov’s elegiac Seventh Symphony – all blurry splashes of harmonic colour and meandering tunes underpinned by dark bass shadows – was so intensely concentrated. In Chopin’s Piano Concerto No 2, Anna Fedorova provided laid-back virtuosity on tap, while the quality of orchestral blend was extraordinary for an ensemble giving its second ever performance. Liudmyla Monastyrska served up a fearsome “Abscheulicher …” from Beethoven’s Fidelio, and Brahms’s Symphony No 4 – conducted by Wilson without score and with serious guts – had raw swagger to burn. 158 days into the Russian invasion of Ukraine, this late insertion into the Proms season was always going to be as much about the humans as about the music. When Wilson turned to the crowd and yelled “Slava Ukraini!” (“Glory to Ukraine!”), before leading an arrangement of the Ukrainian national anthem, there were both roars of delight and tears brushed away. Available on BBC Sounds until 10 October. The UFO are at the Edinburgh International festival on 6 August and Snape Maltings Concert hall on 8 August and tour until 20 August.