Mallinson originally trained for the Anglican priesthood at St Chad's College in Durham. He took a break from his studies to join the Army in 1969, joining the King's Own Royal Border Regiment as a second lieutenant on probation, and he served with the infantry in Cyprus, Malaysia, Northern Ireland and Germany. He was confirmed as a second lieutenant in 1970, promoted to lieutenant on 11 February 1971, and promoted to captain on 11 August 1975, and acting major on 1 September 1979. He transferred to the 13th/18th Royal Hussars on 28 October 1980, and was promoted to substantive major on 30 September 1981. He served in Whitehall, Norway, and Cyprus and Germany again. He was promoted to lieutenant colonel on 31 December 1988 (with seniority from 30 June 1988), commanding his regiment from 1988 to 1991. He was promoted to acting colonel on 1 December 1982, and to substantive rank on 30 June 1993 and brigadier 1 September 1999. His last Army appointment was as the British Defence and Military Attaché in Rome. He retired on 16 March 2004.

Hervey series

The Hervey novels are similar to the Sharpe novels of Bernard Cornwell, although Hervey is a "proper" officer and not raised from the ranks, in the cavalry not the infantry, and campaigning mainly after (not during) the Napoleonic Wars. In UK hardback publication order, the Hervey novels are:

1. A Close Run Thing (1999): Cornet Hervey's adventures before and during the Battle of Waterloo.
2. The Nizam's Daughters (2000): Hervey in India, defending the fictional princely state of Chintal (published in the US as Honourable Company).
3. A Regimental Affair (2001): problems in the regiment in England and Canada.
4. A Call to Arms (2002): back in India, an independent excursion on the borders of Burma.
5. The Sabre's Edge (2003): set in the First Burmese War in 1824, and the siege of Bharatpur in 1826.
6. Rumours of War (2004): Hervey in Portugal in 1826, with flashbacks to the Peninsular War before the battle of Corunna in 1809.
7. An Act of Courage (2005): Hervey imprisoned at Badajoz at Christmas 1826, with further flashbacks to the Battle of Talavera in 1809 and the Battle of Badajoz in 1812.
8. Company of Spears (2006): Hervey in the Cape Colony in 1827 fighting the Zulus, immediately before the death of Shaka and the accession of Dingane.
9. Man of War (2007): England 1827: Matthew Hervey is fighting for the honour of the Light Dragoons.
10. Warrior (2008): 1828 - Hervey is tasked with escorting an embassy to Shaka, King of the Zulus, whose motives are under suspicion.
11. On His Majesty's Service (2011)

Non-fiction

• Light Dragoons - a non-fictional history of the four light cavalry regiments of the British Army. It was published in 1993, soon after he relinquished command of 13th/18th Royal Hussars (which includes (in merged form) two of the light dragoon regiments: the 13th was originally raised as a heavy dragoon regiment in 1715 but later converted to light dragoons; the 18th was raised as a light dragoon regiment in 1759; both retitled as hussars in 1861, merged together in 1922 and then merged with the 15th/19th The King’s Royal Hussars to form the present Light Dragoons in 1992).
• The Making of the British Army: From the English Civil War to the War On Terror (2009). The book examines nearly 500 years of the British Army and examines how its military actions has made it one of the most effective fighting forces in the world today. Mallinson demonstrates how people and events have shaped the army's development. Sections include: how Marlborough's victory at Blenheim is linked to Wellington's success at Waterloo; how the desperate fight at Rorke's Drift in 1879 underpinned the heroism of the airborne forces in Arnhem in 1944; and why Montgomery's momentous victory at El Alamein mattered long after the Second World War.