A formula he developed was utilized to save Westminster Hall from destruction by wood-boring beetles, while others were used to control lice in the trenches during the First World War.

[3] Harold was sent to school in Church Hill House in Crondall where one of his contemporaries, although a boarder unlike Maxwell-Lefroy, was Claude Grahame-White.

Oddly he did not join the Natural History Society at school, contemporary members of which included William Keble Martin, Arthur Hill, and Lawrence C.H.

He finished school in 1895 and joined King's College, Cambridge, receiving a BA in the natural science tripos with first class in 1898.

Before he left Barbados he got engaged to Kathleen Hamilton O'Meara, daughter of a former Provost Marshal in British Guiana from a Catholic family, leading to some disapproval from his mother and sister.

From 1915, five such meetings were held at the Imperial Agricultural Research Institute, and these formed the foundation of entomological knowledge in India.

Among his last works in India was an analysis of the role of birds in agriculture, written along with supernumerary entomologist Charles W. Mason.

He returned to Pusa on 29 July 1912 and an offer was made to retain him but he decided instead to take up a position at the Imperial College as professor of entomology.

[13][14] Maxwell-Lefroy moved to live initially in Strawberry Hill, and later Acton Lodge in Isleworth close to his workplace in South Kensington.

In 1913-1914, Lefroy was consulted by Frank Baines, Principal Architect of the Office of Works, to study ways of exterminating death watch beetles that had been found in Westminster Hall, beside England's Houses of Parliament.

He began to try out various chemicals and finally came up with a 50% dichlorobenzene, 47% mineral oil and 3% barium oleate mixture to brush the wood with.

Ansorge, magistrate and collector in Bihar and Orissa; and an amateur entomologist, he wrote a Report on an Inquiry into the Silk Industry in India (1917) in three volumes but not without a major interruption.

[3] While in Bangalore on the silk study, on 17 April 1916, he received a telegram from the government seeking help on fly control in Mesopotamia.

He published on his investigations into the control of flies and other pests, a note in the Agricultural Journal of India included a photograph of his assistants from Pusa.

In October 1917 he sailed to San Francisco and then to Sydney where he examined the wheat weevil problem along with W.W. Froggatt, the Government entomologist and suggested various measures.

He encouraged their studies and when Cheesman set off for South Africa, he emphasized the need for anyone interested in insects to spend time in the tropics to fully appreciate the subject.

He helped in the production of several short films dealing with insects including one on wasps and another on tiger beetles in a series called Secrets of Nature.

His position at the Imperial College was taken up by Balfour Browne who ensured that the flasks with unknown chemicals that Maxwell-Lefroy was working with were buried.

The only child who survived was Cecil Anthony (d. 1995) who became a general manager of Burmah Oil Company and was later made CBE.

He wrote an unfinished memoir on the life of his father which was posthumously edited as a biography published in 2015 by Laurence Fleming.