Nope. You think you just wave a passport and they let you in without any vetting at all? Try it....you have a commonwealth passport, that should be a magic ticket right? Wave a Syrian passport at Heathrow and you'll be spending some quality time in a room with some nice people answering some questions.
That's not how it currently works. If you come by train, or bus, or boat from continental Europe you don't show your passport to anyone. There isn't anyone there to check your passport. Once you're in Europe, you have a free pass to Great Britain. This is how Brexit came about.
I have landed in Paris, passed through customs and immigration without so much as anyone looking up from their desk. Then to Belgium, back to France, then to England, then Scotland, then Ireland and back to Canada. Entering Canada they checked my passport. I had not a single stamp from my excursion.