Numbers add up in the island’s favour

When just one passenger on a handful of flights and two ferries in July could ruin the island’s hard-earned streak of zero cases and start a new series of infections the travel trial adds risk.

But this has never been about zero risk. Short of refusing entry to freight ships and closing the airport the borders have always had some porosity, and therefore threat.

Not for the first time, Gavin St Pier yesterday asked islanders to trust the leadership team. Public Health has looked at the numbers, assessed the risks and feels they are low.

Doing the maths, it can be seen why.

For a start, the chances are that 1,376 people will not come. Either the boats or the planes, or both, will not be full.

More significantly, the estimated infection rate in England is 1 in 1,700 people and dropping. Even a handful of positive cases would be unfortunate, especially as this trial is aimed at Guernsey residents, not UK tourists.

Factor in that those who know or fear they are one of the 33,000 active cases in England (or further afield) should not be looking to travel to Guernsey or anywhere else and the risk goes down further.

Dr Nicola Brink says she is most worried about the passenger who picks up Covid-19 in the taxi or train or at the airport or ferry terminal on the way to Guernsey.

They will not test positive on arrival, nor show symptoms. Thankfully, they still have to self-isolate for at least a week before being tested.

At the end of those seven days, eight out of 10 will either have the disease and test positive or they will be in the (almost) clear.

And there, in the two out of 10 who get it late, comes the danger.

So the risk is very low and the trial will almost certainly succeed.

But then what? This system helps those who have an urgent need to travel, such as seeing an ailing relative, and don’t mind a week indoors. The numbers will be small.

It is a first step on a journey, but the destination remains unclear.