Leopold Henry Collinson was born in Palmerston North on 13 May 1878, the son of Frances Elizabeth Gittings and her husband, Henry Clement Collinson, a carpenter, professional photographer and farmer. After attending Campbell Street School, Leo was employed at the United Farmers Co-operative Association department store in The Square. When the Wellington firm of C. Smith opened a Palmerston North branch, Collinson joined their staff.
In 1904 Collinson formed a partnership with John Cunninghame, an experienced draper, with whom he had worked at United Farmers. On 4 August they opened a tiny drapery and clothing store in rented premises. They had to raise £900. Collinson scraped together his share by selling stock he owned on the family farm and borrowing against his life insurance; his father invested £300 as a sleeping partner. The store opened with a staff comprising Collinson, Cunninghame and one boy.
On 16 August 1905, at Palmerston North, Leo Collinson married Alice Mary Flood who had worked with him at C. Smith. He delayed his marriage till he was certain that his business was going to flourish. The couple had two sons, Keith and Eric, both of whom later worked for the firm.
Collinson was cautious, but progressive. By 1920 the store had its own electricity generator and a pneumatic cash system. Tearooms, with live background music, became a social focal point from 1915, and seasonal fashion parades were a feature from 1926. From 1919 generations of children were entranced by the Christmas 'Magic Cave' where mechanically animated characters and animals stood in rainbow-lit scenery. The Palmerston North Plunket Society branch used a room in the store for many years until its own building was opened in 1929, and in 1924 the Manawatu Radio Club opened the pioneer local station (2ZF) in Collinson and Cunninghame's. By the time of Cunninghame's death in 1935 the greatly expanded business was a leading Palmerston North department store.
Collinson played an active role in the local community. Through membership of the Palmerston North Chamber of Commerce, the local retailers' association and the Milson Aerodrome committee, he promoted the city's commercial progress. A Rotarian for 28 years, he was president of the local Rotary Club in 1928–29. From its opening in 1928 he took a deep interest in Massey Agricultural College, serving as a co-opted member on the board of governors.
Collinson's main recreational interest was horses. Jumping was his specialist event and he was a keen competitor. Later he bred and trained racehorses. His outstanding horse was Foxiana, who won both the Wellington Steeplechase and the Grand National Steeplechase in 1942. He was president of the Manawatu Racing Club and a longtime member of its committee. In 1922–23 he was master of the Manawatu Hunt, and he was president and committee member of the Manawatu and West Coast Agricultural and Pastoral Association. He was for years marshal of the grand parade and steward for the horse section, and fostered the pony section and the formation of pony clubs.
After Leo Collinson's death at Palmerston North on 25 January 1954, staff mounted a special memorial display in the store's front windows. Alice Collinson had died three years earlier, and he was survived by their two sons. By this time the firm owned all its land and buildings freehold, and employed 100. There were staff dances and picnics and staff sports teams. Two more generations of both the Collinson and Cunninghame families were subsequently involved with running the company. Many loyal employees qualified for gold watches that were presented for 21 years' service.
Throughout his life Collinson had been industrious, 'with a happy disposition and a firm resolve to live a life with justice and integrity as the guiding star'. Although Collinson and Cunninghame's business was purchased by the Farmers Trading Company in 1983, the Collinson name is commemorated in the city. A life-sized bronze horse, by sculptor Artur Volkmann, was a feature in the store. In 1983 this was given to Palmerston North by the Collinson and Cunninghame families and stands in the city's Convention Centre. A tree-lined avenue on campus at Massey Agricultural College was planted and named for Leo Collinson after his death. This no longer exists, but a new Collinson Road was created in 1982.