All the best ideas come from visiting pubs. The famous light bulb clicked on when I went to the Duke of York near Potters Bar, with an old sign across the road announcing “Great North Road”.

Research showed that the pub is an old coaching inn, named after the Duke of York who led Edward IV’s troops in the Battle of Barnet in 1471, one of the key confrontations in the Wars of the Roses.

To my astonishment, as I looked further into the history of the Old North Road, I found that many coaching inns have survived. As a result, I am now working on a book on the subject, which will take me from London to Edinburgh, with many stops to take on water in between.

The road was started by the Romans and became a vital link between north and south when Henry VIII created a postal service. Taverns sprang up to provide post boys on horseback with accommodation. The taverns developed into substantial inns during the great days of coach travel, which ended abruptly in the 19th century with the arrival of the train service.

The great inns in central London have disappeared. The Angel, Islington, was such an important departure point for those – including Nicholas Nickleby and Tom Brown – heading north that the area was named after the coaching inn that once stood there.

You can easily spot an old coaching inn thanks to the large entrances and courtyards at the side through which the coaches came rattling in. Barnet once had several inns, and two are still standing on the high street.

The Old Mitre Inne is a delight, with an unspoilt interior of old beams and wooden floors. The back room includes a portrait of Charles Dickens, who based Oliver Twist in Barnet and used the inn to describe the occasion when the Artful Dodger took Oliver to a pub.

Across the road, the Red Lion, with the giant figure of a lion standing proud above the entrance, was a major inn in its day. Sadly, a modern pub company has modernised the interior, with encased beams, bright lighting and modern furniture, though old photos of the area are worth seeing.

More inns can be visited without straying too far from St Albans. Old Welwyn may be little more than a village these days but it boasts two coaching inns. Stevenage has one surviving inn while the market square in Biggleswade has two. The massive Crown Hotel is currently closed while it’s refurbished by Wetherspoon and, fingers crossed, I trust the pub company will be sensitive to the inn’s origins.

On the other side of the square, the New Inn is a rambling, beamed and timbered building with a large courtyard to the side. It’s owned by Greene King, who has just installed a small brewery where house beers will be produced: you can’t get much more historic than that!

Huntingdon has two contrasting inns. The George, another Greene King hostelry, is vast, proving just how large some inns were in order to cope with the daily arrival of coaches and weary passengers anxious to refresh themselves outside and in.

The Falcon is much smaller and a delight, with a long courtyard, a plethora of wood and beams inside, and a warm welcome from staff and locals.

Strictly speaking, Huntingdon isn’t on the Great North Road or the modern A1. It’s on another ancient route, the Old North Road, but the two merge just north of the town and I’m keen to include it as a result of its Cromwell connections: a relative of Oliver’s ran the George and the town has a splendid museum dedicated to the Civil War.

The journey will continue north. I look forward to revisiting the George in Stamford, with its renowned “gallows” inn sign straddling the road. Forty coaches a day used the inn in the heyday of coaching and I shall rest a while there before heading on to the delights of York.

And, by the way, Dick Turpin never did ride Black Bess to York. But I don’t want to give away too many good stories...