In the 1970s Tonie and Valmai founded Major and Mrs Holt's Battlefield Tours. At the beginning of the 90s the Holts sold their company in order to concentrate upon writing and embarked upon a series of Battlefield Guidebooks that incorporated what they had learned from conducting thousands of people around battlefields.

The series, Major and Mrs Holts Battlefield Guide to... incorporates detailed travel directions, military history and fascinating anecdotes collected over a quarter of a century. The books are designed as companions for travellers whether sitting at home or physically visiting the battlefields and are written from a male and female point of view thus encompassing the human element of war through the literature and poetry of the period.