The madness, because that is what it is, began in earnest in 1998 with the publication in the respected British medical journal The Lancet of a study purporting to establish a link between autism and MMR — the vaccine that protects against measles, mumps and rubella.

For defenders of the right to free speech — and anyone who read these pages last week will know that I am one — the encrypted messaging app Telegram presents something of a conundrum.