I hold dual Chinese and Canadian citizenships. Last year, I was returning to China from Canada, but the only available flight option was a transfer flight with a layover in London. Upon passing through UK customs, I accidentally used my Canadian passport instead of the Chinese one.

However, since China does not recognise dual citizenships, I was forced to use my Chinese passport when exiting the UK. Hence, I entered and left the country using different passports.

I was wondering if this would cause any potential problems if I wish to return to the UK. Do UK customs keep track of exit records? Could they deny me entry next time? Would I be considered as an undocumented immigrant?