David Deutsch (DD) wrote in Quantum theory, the Church-Turing principle and the universal quantum computer (1985), p. 3:
Church (1936) and Turing (1936) conjectured ... This is called the ‘Church-Turing hypothesis’; according to Turing,
Every ‘function which would naturally be regarded as computable’ can be computed by the universal Turing machine. (1.1)
And from Deutsch's references (p. 19):
Turing, A. M. 1936 Proc. Lond. math. Soc. Ser. 2, 442, 230.
Now we'll compare with Turing's paper: On Computable Numbers, With An Application To The Entscheidungsproblem (1936), p. 230:
the computable numbers include all numbers which could naturally be regarded as computable.
Turing wrote "numbers", but DD misquoted that as "function". Turing also wrote "could" which DD misquoted as "would".
There's also a problem because Deutsch uses what appears to be an italicized block quote. You'd expect the whole block quote to be a quote of Turing, but instead it's a paraphrase. Inside the paraphrase are quotation marks surrounding the misquote of Turing that I criticized.
DD's citation is also incorrect. DD cites Turing's paper to volume 442 of the Proceedings of the London Mathematical Society, but it was actually in volume 42 not 442.
To determine what's correct, we can check how Turing himself cites it. In a correction to his paper, Turing cited himself:
Proc. London Math. Soc. (2), 42 (1936-7), 230-265.
You can also see that the latest volume of the journal, published in 2021, is volume 122. Volume 442 is unlikely to exist for over 100 more years. And the journal's website has archives showing that the Turing article was in volume 42.
Tangentially, I hope this lowers your opinion of academic peer review. DD's paper was published in Proceedings of the Royal Society of London, a prestigious and peer-reviewed journal that started in around 1830. It has published work from many famous scientists.
Thanks to Dec for finding this misquote.
Note that DD has published a lot of misquotes.
Update 2021-07-15: Dec pointed out that a similar Turing misquote is in DD's book The Fabric of Reality:
He [Turing] conjectured that this repertoire consisted precisely of ‘every function that would naturally be regarded as computable’.
No, Turing wrote "all numbers which could" not "every function that would".
It appears that DD got this misquote from his own paper, and also modified it. There's a recurring pattern where every time DD touches a quote, there's a significant chance that he changes something. Here, he took the word "every" which was outside of quote marks in his paper and moved it inside quote marks for his book.