It was probably the one factor that Boris Johnson did not take into account when choosing December 12 for a General Election – tide times.

But it has been revealed that low tides forecast for polling day could mean that votes in the Isles of Scilly will not be counted until the following day.

Votes on the Islands are transported to St Mary’s after polling stations close, but that may not be possible on December 12 and so the count could be delayed.

It was only recently that votes have been counted on St Mary’s. In the past ballot boxes were locked up in the local police station cells and then transported to the mainland to be counted.

Because of this the St Ives constituency – of which the islands are part – was one of the last to declare its result as it had to wait for the boxes to arrive.

Mark Boden, interim chief executive of the Council of the Isles of Scilly, said that boats will be ready to transport the votes from the off islands to St Mary’s but they could be halted by the low tide.

And it’s not just low tides which could affect the transportation of votes, with the weather also being a factor.

Five of the islands are inhabited and ballot boxes will have to be taken to St Mary’s for counting. It had been suggested the votes could be counted on the individual islands if necessary, but it is not practical to do that.

Andrew George, Liberal Democrat candidate for St Ives, said that safety was more important than the speed of getting a result.

He said: “I’m aware this issue arises from time to time. Especially when low tide coincides with the 10pm close of poll. In the past the election never started in St Johns Hall until all boxes, even from the off islands, had arrived at Penzance the following morning.

“Apparently in recent years, anxiety about the speed of getting results out has become more important than making sure it’s done properly and safely. The speed of the result has never been a high priority for me.”

Mr George said he was planning to visit the Isles of Scilly during the election campaign but could not be certain it would happen due to the weather.

The other candidates in St Ives are Derek Thomas, Conservative; Alana Bates, Labour; Ian Flindall, Green Party; John Harris, The Common People; Robert Smith, Liberal Party.