It all started to go wrong when they substituted "Jubilee Line" for the perfectly good working name of "Fleet Line".
Indeed!!
That may have had a quiet a lot to do with the final Jubilee line route being quite different to the original plans which ran under Fleet St to the City of London.
That's not the reason. Firstly, the initial portion did end up pointing towards Fleet Street, terminating at Charing Cross (with continuation/over-run tunnels under Strand ... almost to Fleet Street in fact); when they subsequently extended it east, they abandoned the part from Green Park to Charing Cross and onwards, and diverted it after Green Park to where it runs now. Secondly, even if the change of onwards route had been known ahead of the initial opening, the plan to call it the Fleet Line anyway wasn't abandoned. Almost right up to the opening, the publicity still referred to the Fleet Line; and the embossed enamel line interchange signs, on existing lines the new line interchanged with, were all made with the name "Fleet Line" for the new line. But at the last minute, the then powers-that-be in the GLC, in a fit of royalist sycophancy, changed the name from Fleet to Jubilee. Stickers had to be put on lots of the signs that were already in place in parts of the network, changing "Fleet" to "Jubilee". They kept the same line colour, but started calling it silver instead of grey!
(Campaigners from a group called MA'AM - Movement Against A Monarchy - spent the first day or so after the opening doing reverse stickering on the line diagrams in the trains themselves, covering "Jubilee" with a sign saying "Fleet Line - don't Jubilee've it!")