Only this isn't entirely true. The cockroaches were certainly very real, but the tax bit isn't. After a post-war low of about 25% income tax paid by the top earner, in the early 1930s that upper level shot up to 65% (and hit a peak during the later years of the second world war of about 94%).
It's reasonable to assume, then, that the Tories want to return to the early part of the 20th century. But there's a flaw with that too: at that time, the standard income tax level was only 2%, compared with 23% now. If Joe and Jenny Pleb aren't paying for the streets to be cleaned and for the police to keep the rabble away from the rich folks' estates, who will? And presumably in the mind of a Tory, we didn't need the police or street cleaners as much back then because the poorest had work to keep them busy - as well as the cockroaches - so they had less time for stealing and whatever else the grubby little urchins might get up to.
This process of elimination has brought me to one of two assumptions about the Tories' economic plans:
1) They want the poor to pay for the police, education, whatever healthcare is left and all council services whilst the rich pay for virtually nothing, or
2) They haven't really thought it through.
Although number one sounds the most plausible, it must be number 2 because they've already taken the poorest workers out of the income tax bracket so they're not paying for very much either.
They clearly haven't got a clue what they're doing.