Holders of Russian-issued full driving licence have to go through theory and driving test in the UK to get UK full driving licence regardless of existing driving experience Driving tests in Russia are similar to UK standards, so requiring drivers to undergo a test again is an unnecessary burden
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Ukraine-issued driving licences were recently allowed to be exchanged to UK ones (https://www.gov.uk/government/consultations/exchange-of-driving-licences-issued-in-taiwan-the-united-arab-emirates-ukraine-and-the-republic-of-north-macedonia)
Driving test standards and road safety levels in Russia and Ukraine are very similar so it makes sense to also allow Russian-issued licences to be exchanged.