Yesterday was the 77th anniversary of his death, on 21 June 1945, his 22nd birthday, when he was clearing German mines and some detonators caused an explosion.
The service was conducted by the Rev. Jan Fowler, who said the island owed Mr Onions so much.
‘It is important for us to remember this young man because he is not on the Roll of Honour because he died when the war was finished,’ she added.
‘We owe him a huge debt of gratitude because he helped make Alderney safe for all the homecomers who were returning and helped make it the place it is today.’
Lt-General Cripwell laid a wreath at Mr Onions’ grave, along with States of Alderney president William Tate and 11-year-old Isabella Simeone, on behalf of St Anne’s School.
‘His Excellency was particularly pleased to see the work that has been recently carried out to make it a more fitting memorial to his fellow Royal Engineer, Sapper Onions,’ said Mr Tate.
‘Some years ago, His Excellency was involved in renovation work to some of the Commonwealth War Graves in St Anne’s Cemetery. He is acutely aware of their significance, and the importance of maintaining their upkeep.’
It was the best turnout the memorial service had seen, Mrs Fowler said, with a range of islanders attending, ranging from school children to a 94-year-old Army veteran Army.
‘All ages were represented which was lovely. It is a very poignant time and it is important that we remember him.’
Lt-General Cripwell also presented Queen’s Platinum Jubilee medals to two senior harbour staff and went on to attend yesterday afternoon’s meeting of the States of Alderney.