Have you ever noticed how coroners are getting younger? I remember an elderly gent, entirely out of touch with reality, it seemed to me, straining forward to question a witness at an inquest in Cambridge. “You say your companion had been drinking brain damage. Er, what exactly is brain damage?” The concoction in question consisted of half a pint of Abbot Ale mixed with a strong bottled beer called St Edmunds. Everybody in the courtroom knew what brain damage was, and why it was not at all surprising that, after an evening drinking it, the deceased had set off on foot along the London-to-Norwich mainline singing its praises. Everybody except the coroner.

And now I find myself, at about the age he was then, asking a similar question. Er, what exactly is Red Bull?

“It’s a high-energy drink,” says the man in the off-licence. I ask if it contains Viagra, but he just laughs politely and tells me the ingredients are listed on the can.

A friend is more helpful. “It’s supposed to be like an amphetamine, only legal,” he says. “Kids drink it with vodka. They reckon it keeps them going, but it tstes dreadful.”

It does, too. Sweeter than Lucozade, only without the yellow see-through wrapper that used to make the world look bright and sunny when you held it in front of your eyes, back in the good old days.

No Viagra then, but plenty of glucose. And caffeine too, although only as much as you’d find in a cup of coffee. But there’s a magic ingredient, of course - an amino acid for which much is claimed, and which has the conveniently bullish name “taurine”.

According to the Red Bull website, taurine acts as “a metabolic transmitter”. It also improves heart function and helps remove toxins from the body. “At times of extreme physical exertion,” it explains, “the body no longer produces the required amounts of taurine, and a relative deficiency results.”

Increased physical endurance, improved reaction time and concentration, and an overall feeling of well-being are just some of the effects claimed for the drink. How it works in combination with vodka isn’t specified.

At the risk of sounding like an elderly coroner, I should also point out that taurine was first identified as a constituent of bile.Ox bile.