A former assistant to Prince William has been selected as the National Party candidate for the safe seat of Ōtaki.

Tim Costley's selection comes after the current Ōtaki MP, former Minister of Primary Industries Nathan Guy, announced he was stepping down from politics earlier this year.

Costley, a Wing Commander overseeing operational airworthiness at Ohakea, joined the Royal New Zealand Air Force (RNZAF) as a pilot in 2001.

He served as an equerry to Prince William during the Duke of Cambridge's 2014 new Zealand visit, assisting him with gifts and accompanying him around Wellington's Civic Square.

He has completed a tour of duty in Afghanistan and a number of rescue missions in New Zealand and humanitarian missions in Fiji and Papua New Guinea.

The seat has traditionally been won by a National candidate, meaning it's very likely Costley will become Ōtaki's next MP.

In the 2017 election, Guy won 20,700 votes compared to the 14,600 won by his Labour competitor.

"The Ōtaki electorate is a real snapshot of provincial New Zealand spanning from Paraparaumu in the South, to Foxton in the North," he said.

"We have some critical challenges here, but we also have some great opportunities."

Costley thanked Guy for being a strong advocate for the Ōtaki electorate since he won the seat back in 2008.

He said getting roading infrastructure completed will be a priority of his.

"The current Coalition Government has cancelled the Horowhenua Expressway from Ōtaki to north of Levin, a project committed to by the previous Government."

Costley has a Master's degree in International Defence and Security, a Bachelor's Degree in mathematical Physics and a Diploma in Business.

In 2014 Tim was seconded to HRH the Duke of Cambridge as an Equerry – an officer of the British royal household who assists members of the royal family.

He is also the founder of The Missing Wingman Trust – a charity which supports Air Force families when someone is killed, wounded, or becomes ill, whether in New Zealand or overseas.