A memorial to commemorate seven airmen killed in a mid-air plane crash 50 years ago is to be unveiled.
The two RAF aircraft hit each other over Holt, Norfolk, on 19 August 1968, in such a fierce explosion that people thought they were under nuclear attack.
No-one on the ground was hurt, but all seven airmen died.
Some of the victims' relatives, who have come from as far away as South Africa and Canada, are due to attend Sunday's memorial at Holt Country Park.
The Victor tanker, from nearby RAF Marham, and the Canberra, from RAF Bruggen in Germany, crashed in the night skies after an electrical storm knocked out the radar system, organisers said.
It was later described in Parliament as a "miracle" that no-one else was killed on the ground.
The New Farm Aviation Heritage Group, which runs a small museum in Frettenham, Norfolk, organised the information board memorial after discovering small pieces of wreckage while being allowed to search the country park last year.
Trevor Hewitt, from the museum, said: "People thought it was a nuclear attack because the resulting explosion was quite tremendous.
"It lit the sky up and wreckage was falling through the cloud base. This caused fires in various places."
It was one of the group's members, a former country park worker, who suggested investigating the 100-acre (40 ha) woodland.
"He went to go to work the next day and was not allowed to go in because there was RAF personnel and police everywhere recovering wreckage," said Mr Hewitt.
"Things like this would undoubtedly disappear into the mist of time if things like this weren't done.
"The crews still have families and need to be remembered... it's going to be emotional."
The unveiling will be followed by an afternoon service at the town's main church.