Never heard this expression before, but I'd just like to point out that there is NO station anywhere in the London Underground system by the name of 'Bakerloo'.
Therefore, I can only assume that the correct phrase is in fact 'Changing At Baker Street". As at Baker Street station it IS possible to change between the Hammersmith And City (pink) and Bakerloo (brown) lines.
Travel safely now...changing at bakerloo or anywhere else you might fancy
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