Looks like it's time to write an engaging historical narrative on...

checks bingo card

...the history of British tax law. Well then. Someone on the floor of Parliament does say the phrase "Pussy Pieces" so it's not all bad.

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One of the big misconceptions around this story and the British VAT (value-added tax) in general is that taxation on luxury items (with odd rules and exceptions to boot) happened at the start of the VAT tax, but its roots are much earlier, during WWII.

January 1940 was when food rationing started, using coupon books. It was not uniquely a British phenomenon -- here's some United States sugar stamps circa 1944 at the Columbus Museum, for instance -- but it went on longer and more memorably than elsewhere with rationing ending only in 1954.

Cojoined with that was a change in financial policy. The one to credit/blame is John Allsebrook Simon, 1st Viscount Simon, Chancellor of the Exchequer when war broke out in 1939. He proposed and eventually got the Purchase Tax, which went through multiple addendums in the years following, but in essence had the goal of reducing use of "non-essential" items (thus saving war resources for essential things) by taxing them. As the Chancellor explained in Parliament:

The tax will put no sort of obstacle in the way of export trade, but we must be resolute in reducing consumption at home. It is the deliberate intention of such a tax as this to do so ... The truth is that we have to face quite boldly the necessity of transforming our home economy for the purpose of helping to win the war, and this cannot be done without drastic and definite action. That may impose sacrifices all round, but we have to face those things so long as they are fairly adjusted between the people.

The Finance Act 1940 (which you can read here) was the result. The main difference between the tax it provided and VAT was it was point-of-manufacture rather rather than point-of-sale; also it made it to an eye-popping 100% in April 1943 for 3 years.

In general, the more "luxury" the item, the higher the tax. Decisions could be made on lobbying rather than reason.

It became the basis for many additions and changes and revisions. For a particularly gnarly example, check out this 1970 list revising an earlier act from 1968 which lists (among other things) "drugs and medicines" to be considered exempt from an earlier tax, and it really just goes on and on and on:

Ferrous fumarate anhdrous;

Ferrous succinate with or without succinic acid

Fluopromazine, and salts thereof;

Flourouracil;

Flurphenazine, and salts thereof;

Folic acid or derivatives thereof, whether or not combined with a salt of iron;

Formintrazole;

Frusemide;

Furazolidone, and its 5-morpholinomethyl derivative

By the early 1970s the tax code was seriously in need of an update.