Chapelle Dom Hue is just off the Catioroc headland and to the south-west of Perelle Bay.
Since the 1970s small bits of pottery and worked flint have been found on the eroding edges of the island, but this will be the first time there has been a modern archaeological dig.
‘There has been medieval pottery found – from the 10th to the 14th century – and prehistoric flint,’ States archaeologist Phil de Jersey said.
‘We’ve been collecting for a long time. What we want to do now is give those finds more context, which is why we will be excavating.’
There are two small islets, covered with grass, which it is believed were once connected but are now separated at high tide.
Dr de Jersey said they would handling the dig very carefully due to the delicate nature of the islands.
‘We don’t want to make the coastal erosion any worse,’ he said. ‘So we will be excavating in the middle.’
The foundations of a small building can be seen in the middle of the islet, but it is not known what it was used for.
Dr de Jersey said it was possible that it was used as a retreat for the monks on nearby Lihou, which could also help explain the name of the islet, which derives from the word chapel.
The islet had been dug once before – in 1893 – but there are no details of exactly what was found.
The islet is cut off when there is a higher than seven-metre tide.
‘We are carrying out the dig on neaps, so we won’t have to worry about that,’ Dr de Jersey said.
It is not known how much soil there is above the granite bedrock, so while the archaeologists are planning a 26sq. m trench, it might not be very deep. The island is not easy to reach on foot but everything will have to be carried over.
The dig will start on Tuesday [29/8] and is expected to last five or six days.