While it is uncertain if Russia’s main Opposition leader Alexei Navalny will still be alive when this appears in print, what is certain is that the widespread suspicion he was poisoned ~ the latest to suffer this fate ~ will not go away.

It is a chilling prospect for those who oppose Russian President Vladimir Putin to live with the realisation that the tea they sip, or the food they ingest, may lead to death or permanent injury.

Certainly, there is nothing to suggest that Mr Putin’s most strident opponent, a well-built, 44-year-old, 1.88 m tall man apparently in the prime of his life, suffered from a condition that would render him comatose if he sipped a cup of tea.

Two facts are not in question. First, Mr Navalny is by far the staunchest critic of the Russian President; he has been arrested many times by the regime and when he decided to contest against Mr Putin in the 2018 election, his candidature was disallowed by election authorities. Second, that those the Russian regime disfavours are often targeted with poison.

Two years ago, Pyotr Verzilov, an Opposition activist slipped into coma in similarly mysterious circumstances and battled death for over a month, until doctors in Germany, where he was flown, managed to save him.

Though no trace of poison was found, Mr Verzilov remains convinced he was poisoned. While German Chancellor Angela Merkel offered similar help to Mr Navalny, and an air ambulance was sent from Nuremberg to fetch him, doctors have said he cannot be moved because his condition is unstable.

Others who believe they were targeted with poison by the Russian regime include Ukraine’s former President Victor Yushchenko, who was left permanently disfigured after being administered industrial dioxin, possibly in a dish of boiled crayfish. The pro-Western politician has always blamed Moscow.

Lacing a cup of tea or food with poison is simple and the person administering it can quite easily cover his or her tracks. Former KGB officers are on record to confirm that use of poison by the Soviets and their successors in the Russian state is quite common.

Certainly, many in India will recall that the widow of India’s second Prime Minister, Lal Bahadur Shastri, had maintained her husband was poisoned whilst in Tashkent in January 1966. Many of Mr Putin’s critics have been poisoned on domestic flights, the attractions of in-flight service often serving as a trap.

Opposition activist Vladimir Kara-Murza slipped into a weeklong coma after taking an Aeroflot flight. Journalist Anna Politkovskaya was poisoned on a flight in 2004. She survived to tell the story of the cup of tea that nearly laid her low, but not for long as she was shot dead in the elevator of her apartment. Mr Putin, a former KGB foreign intelligence officer, has much to answer for but it is unlikely he will ever be questioned.