Leyland [formerly Naylor], Christopher John (1849–1926), naval officer and silviculturist, was born at Liscard, Wallasey, Cheshire, on 19 September 1849, the eldest son in the family of three sons and seven daughters of John Naylor (1813–1889), a partner in the family's Liverpool bank, Leyland and Bullins, and his wife, Georgiana (d. 1909), the daughter of John and Charlotte Edwards of Ness Strange, Shropshire. While he was still an infant the family moved to Leighton Hall near Welshpool, Montgomeryshire, the estate his parents had been given as a wedding present and which his father set about extending to some 4000 acres and improving in lavish style, employing the landscape architect Edward Kemp. He grew up at Leighton, across the Severn from Powys Castle, between the Long Mountain and the river, amid the gardens, model farms, forested hillside, and the new church, school, cottages, and workplaces that the Naylors' enlightened ownership bestowed.

Naylor inherited a love of the sea and sailing from his father (a member of the Royal Yacht Squadron and owner of the schooner Sabrina) and after preparatory school entered the navy as a cadet on the training ship Britannia at Dartmouth, aged thirteen. Two years later he sailed as a midshipman on the Victoria, the last of the three-deckers, fitted with steam engines giving her a speed of 13 to 14 knots, which was flagship of the commander-in-chief, Mediterranean. He saw brief service in the Pacific before joining the sleek wooden screw frigate Liverpool, flagship of Admiral Hornby's flying squadron. His final posting was to the China seas in temporary command of a gunboat. He retired from the navy in 1872 as a sub-lieutenant. On 22 October 1874 he married Everhilda Elizabeth (1851–1890), daughter of Ralph Creyke of Rawcliffe Hall, Yorkshire: they had two daughters. Their home was at Trelystan, close to Leighton Hall. While he was nominally a partner at Leyland and Bullins bank from 1879 until 1901 (though latterly not active), and a Montgomeryshire JP, his chief interest was in forestry and extending the Leighton plantations.

At his father's death in 1889 Naylor inherited the Leighton and Brynllywarch estates, which he eventually made over to his brothers and their heirs, as in 1891, on the death of his uncle Thomas Leyland (formerly Naylor), he also inherited the Haggerston Castle estate at Beal in Northumberland: to do so he changed his name from Naylor to Leyland in 1891 (obtaining a royal licence for the change on 30 December 1893). The litany of deaths had included his wife and one of their daughters. Accompanied by his surviving daughter, Hilda, he went to live at Haggerston. On 1 March 1892, in York Minster, he was married for the second time, now using the name Christopher John Leyland, to Helen Dora (1860–1940), the eldest daughter of the late Digby Cayley of Norton Grove, Malton, Yorkshire. His son and heir, Christopher Digby Leyland, was born on Christmas eve 1892, followed by two more sons and three daughters.

Soon after its founding in 1894 Leyland became a director of the Parsons Marine Steam Turbine Company and shared in the financing of Charles Parsons's experimental turbine-powered vessel Turbinia, launched into the Tyne in August that year. Leyland became deeply involved with Turbinia's development, acting as captain of her ten-man crew throughout her speed trials, when she eventually attained speeds of well over 30 knots, considerably outpacing any ship in the navy. At speed all that could be seen of the sleek, 100 foot long ship was her 'bow emerging from a huge wave and a flame from the funnel flickering into the air' (Smith, 14). He captained Turbinia on her audacious appearance at the queen's diamond jubilee fleet review at Spithead on 26 June 1897 when she gave a brilliant but unauthorized display, which was eventually to convince the Admiralty of the virtues of steam turbines, and also on two eventful trips to Paris for the 1900 Universal Exhibition, and a triumphant demonstration for the French navy.

At Haggerston Leyland's energies knew no bounds, as he set about the rebuilding of the huge mansion and the improvement of the estate in such a manner as his father had at Leighton. Haggerston Castle was remodelled and enlarged by R. N. Shaw between 1892 and 1897; a Parsons turbine was utilized for heating and lighting; and a tower of a similar design to one at Leighton Hall was built for holding tanks of spring water for the estate water supply. The tower also housed his observatory, where he pursued his interest in astronomy. There were well-equipped stables, kennels, workshops and garages for a collection of early motor cars, a menagerie with exotic deer and cattle, ostrich and bears, walled gardens and greenhouses, a palm house, and an arboretum, as well as extensive woodland plantings and lavish Italianate pleasure gardens ornamented with lakes and balustraded terraces, temples, and statues. After a disastrous fire at the mansion in November 1911 he had it rebuilt in even more dramatic style by James B. Dunn; it was requisitioned as a military hospital during the First World War. Leyland made his home at the dower house, The Mead, Beal, Northumberland, where he died of cancer of the prostate and exhaustion on 21 October 1926. The Haggerston estate, together with everything removable from the mansion and the gardens, was dispersed at a sale in 1931, though some of the estate buildings, including the observatory tower, and parts of the gardens and woodlands survive in and around the Haggerston Castle Caravan Holiday Park.

Leyland was buried in the churchyard at West Kyloe, Northumberland, with cypresses C. leylandii planted nearby. Though little noticed in his lifetime, the cypress that took his name was to prove a controversial horticultural legacy. In 1888, in the pinetum at Leighton, he had noted six seedlings of Nootka cypress (Chamaecyparis nootkatensis) of unusual characteristics from their accidental cross-pollination from a Monterey cypress (Cupressus macrocarpa) growing in the vicinity. These parent trees from Alaska and California respectively would never have met in the wild. He took some of the cypress seedlings to Haggerston, where they tolerated the winds from the North Sea and grew as happily as at Leighton, showing an amazing rate of growth, as much as a metre a year. As the bigeneric seedlings were sterile they were propagated vegetatively: the offspring were eventually to be named Cupressocyparis (Cupressus x Chamaecyparis) leylandii. In 1925 the Royal Botanic Garden at Kew recognized Cupressus x leylandii (published in the Kew Bulletin of 1926, but transferred to Cupressocyparis leylandii in 1938).

Cupressocyparis leylandii and its clones named ‘Haggerston Grey’, ‘Leighton Green’ and ‘Naylor's Blue’ were massively promoted by the forestry interests for their virtues: rapid growth (55 to 60 feet in twenty-five years); tolerance of salt winds; hardiness to the worst winters; and suitability for shelter belts. They made an excellent hedge if kept at about four feet because mechanical trimming produced no ill-effects. The leylandii were given Royal Horticultural Society awards in 1941 and 1969, and were promoted into gardens to satisfy demands for ‘instant’ shelter and privacy, especially during the second half of the twentieth century. The virtues remain, but leylandii now often find themselves derided as weeds and hated as sterile interlopers; but they are merely plants in the wrong place.