Two towns separated by two continents have spent a weekend celebrating their rock-solid archaeological bond.
Thetford and Nagawa, Japan have common ground in their historic use of flint and obsidian.
Now representatives from Norfolk and Japan have commemorated the towns' bond with the world's first twinning of archaeological sites – between the Neolithic flint mines at Grime's Graves, and the Hoshikuso Obsidian Mines near Nagawa.
Jan Summerfield, English Heritage's curator for Grime's Graves, said: 'It was a wonderful occasion and fantastic to see so many people come together to celebrate it.
'We have already enjoyed some fantastic educational and cultural exchanges between Grimes Graves and Nagawa-Machi and we look forward to working with them more in the future.'
The twinning ceremony at the flint mines on Thursday, July 14 was at the centre of a three-day series of cultural events, including a conference in the Carnegie Room in Thetford of Friday which featured guest speakers from the British Museum, University of East Anglia and University of Tokyo.
The conference was organised by a range of groups including the Ancient House Museum, the Brecks-Nagawa Exchange Committee, and the Sainsbury Institute for the Study of Japanese Arts and Cultures (SISJAC).
Dr Simon Kenar, from SISJAC and UEA, said: 'It is wonderful to be able to celebrate the ways that we can encourage international collaboration in these troubled times.'
Of the twinning, he said: 'This is not only a first for Norfolk but a first for the world, and that is rather exciting.'
Ms Summerfield said the conference had been a 'huge success'.
'I am very excited by the prospect that we are going to make further links with other towns in Japan.'
A Flint and Obsidian families fun day also took place in the King's House gardens on Saturday, giving visitors the chance to watch flint knapping and demonstrations of Jomon (Japanese Neolithic) cookery.
The Flint Rocks! exhibition by Breaking New Ground, which reveals Thetford and Brandon's links to the flint mining industry, has been on show at the Ancient House Museum since November and runs until October 29.
The exhibition features items from the Obsidian Museum in Nagawa, with which Ancient House has had a friendship agreement since 2012 and which its Teenage History Club visited last year.
Museum curator Oliver Bone, who attended the conference, said: 'It has been brilliant. All the comparisons between the Japanese experience and the internationally important pre-history of this area was wonderful to hear.'
Melissa Hawker, learning officer at Ancient House Museum, said: 'All the events were drawing on the idea of twinning sites that have great similarities even though they are on the other site of the world.
'We had many angles on this project – from academic to academic, young people's involvement, and the global partnerships.
'It has been a very exciting thing to be part of and hopefully it will continue for many years to come.'
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