Conversely - what I did WRONG...
On a normal weekday, I needed to get from Kings Cross (arrived 0804) to Paddington (wanting to catch the 0903 to Newquay), and an information board showed that the Circle and Hammersmith&City were out-of-action because of a broken-down train. The gateline staff at KX/StP Circle-line barriers said "Victoria Line to Oxford Circus, then Bakerloo to Paddington". Crush-loaded - not really appropriate for a family of 2 adults and 2 children (ages 9 and 11). We did catch the train (*), but it was all a bit fraught.
Next time, it'll be Thameslink to Farringdon, then Elizabeth Line. It's even better on the return journey, as the escalator up from the Elizabeth Line at Farringdon leads straight to the Northbound Thameslink platform.
(*) Only for it to be cancelled at Plymouth because of Goss Moor bridge being hit again.