Police say the man, who's not yet been named, died at around 6.40pm on 18 September.
Police say the 66-year-old died in a single vehicle accident on the track to Fort Clonque, at Alderney's south-western tip.
They say as investigations are carried out there will be a police presence in the area and ask people to stay away.
One of Britain’s rarest fungi has been found on Alderney
A species of fungi classed as Vulnerable on the IUCN Red List has been recorded on Alderney for the first time.
Channel Islands' parliamentary Standards Commissioner resigns
Dr Melissa McCullough, the joint commissioner for Jersey and Guernsey, made the move after deputy Gavin St Pier easily won a vote into his conduct.
Guernsey Deputies vote not to suspend St Pier
Guernsey's Vice-President for Policy & Resources has comfortably avoided suspension after twice the number of deputies voted against the Commissioner for Standards' recommendation.
States of Guernsey chief exec apologises for IT system failures
Boley Smillie says - after £42M was 'wasted' in States IT project 'failures' - he will investigate what happened to restore public trust.
Areas of Guernsey's States IT transformation branded 'shocking waste of public money'
Deputy Gavin St Pier has launched a scathing attack on poor management and decision-making around government initiatives that cost £42M.
Guernsey's Liberation Day 2026 celebrations to be more low key
Organisers say the Cavalcade and St Peter Port activities will continue but individual parish celebrations may not happen.
Guernsey's Sexual Offences Law to include AI related crimes
Home Affairs says legislation needs to be capable of dealing with new offences where AI is used to fake images.
Lloyds Bank Foundation opens 'unrestricted funding' for all CI charities
After a record year of charitable funding, Lloyds Bank Foundation will now give money to local causes to use how they see fit.
