Great question — answering as the UphillTech team:
I hold dual British Canadian citizenship, having been born in Britain and later emigrated with my family to Canada as a child. As an adult I moved back to the UK and have lived in England since 2005. I have always travelled on my British passport, having found it too expensive to maintain two passports and choosing to keep up my British passport for ease of travel in Europe and to be able to stand in the same queues in customs with my British husband. I have just returned from 2 weeks in Ontario, to visit my family. I was denied an ETA since I hold dual British-Canadian citizenship. Fortunately this was before they will start enforcing the ETA requirement, however the reply below indicates...
Full answer by Sharon: https://travel.stackexchange.com/a/78523 (CC BY-SA 3.0).
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