Sir Trevor Garland, who served as honorary consul to the Solomon Islands for almost 20 years, was arrested by police in Sydney on Thursday.

He was charged with four counts of aggravated sexual assault and refused bail, to appear at Central Local Court on Friday.

The 62-year-old was arrested when he attended Kings Cross police station at about 9am on Thursday.

An hour and a half later, detectives raided his sprawling Oakhurst historical home, "The Oaks", which was once listed as the address for the Solomon Islands consulate in Sydney.

It is alleged Sir Trevor sexually assaulted a 24-year-old man at the home between March and April 2017.

Officers from Strike Force Moorooba, set up to investigate the assault allegations, seized "a number of items" from the double-storey Victorian mansion.

Sir Trevor was made a Member of the Order of Australia in 1991 and has been bestowed other awards, including Member of the Order of the Solomon Islands in 1993 and the Cross of the Solomon Islands in 2009.

In 2010, he was appointed a Knight of the British Empire for contributing to the development of the Solomon Islands.

He was knighted by Prince Charles at Buckingham Palace on November 19, 2010.

In online profiles, he lists his involvement in St Vincent's Hospital's "ten bed" program, which brings ten seriously ill Solomon Islanders to Sydney each year for free medical treatment.

In a 2015 newsletter, the hospital said the program was facilitated by Sir Trevor, who liaised with local Solomon Islands doctors to choose patients based on medical need.

It said Sir Trevor communicated with relevant specialists at St Vincent's, who then accepted care of the patients.

"The Ten Bed Program has been in place now for over two decades and exists with the generous support of the Sisters of Charity and Sir Trevor Garland and the Solomon Islands Consulate," the newsletter said.

Police said anyone with information or concerns should contact Crime Stoppers on 1800 333 000.