William Costello was born in Flint on 24th July, 1886 and baptised on 8th August, 1886 at St Mary’s Catholic Church, Flint. He was the eldest of nine children to Patrick Costello and Ellen (McManus) and the brother of  Private Peter Patrick Costello.

William was raised in 17, Princes Street then the family moved to 35, Mumforth Street until settling at No. 59.

He could not be located in the 1911 census; however, in 1901 his occupation was listed as ostler (groom) at an hotel. He was unmarried.

He enlisted in Flint on 14th August, 1914 and joined at Wrexham the same day. His medical record stated he was 5ft 71/2 ins tall. He landed at Gallipoli circa June 1915 and subsequently posted to Mesopotamia, where he was killed in action on 3rd February, 1917.

He has no known grave but is commemorated on the Basra Memorial, Iraq, on Panel 15. He is remembered on two war memorials: Flint Town and St Mary’s Catholic Church, Flint. He is also commemorated on the North Wales Heroes’ Memorial Arch, Bangor.

He was awarded the 1914–15 Star, British War Medal and Victory Medal.