Briefly dip into England to go to Berwick upon Tweed.
Between Kelso and Coldstream the National Route and the Tweed Cycleway go different ways. The National Route is the better choice, but using both to make a circular route would be an attractive day trip.
Coldstream like Gretna is right next to the Scottish border, and like Gretna has an 'Old Marriage House' for similar reasons. Coldstream is attractive too, maybe not so elegant as Kelso but the park by the river is a good place to picnic. The Coldstream Guards were established here and eventually became the 'Kings Men'. Quite near too is The Hirsel, former home of Sir Alex Douglas Home and a bird sanctuary.
The River Tweed is the border now between England and Scotland. This used to be the case all the way to the sea but Scotland didn't manage to hang on to Berwick, it was finally surrendered to England in 1482. This made for the odd situation of Berwick not being in Berwickshire.
The route rolls along through fairly flat country crossing the Tweed near Norham. There's a castle just outside Norham and a pub doing bar lunches in the centre. We cross over into Scotland again on the romantic Union Suspension Bridge, the first of any size in Britain. Before that you pass a honey farm. This has a visitor centre where you can see the bees in action and also buy honey.
Shortly after there's Paxton House, one of the best Adam Mansions in the country. There's a romantic story attached to it. On the 23rd August 1750 the heir to Paxton estate, Patrick Home, pledged his love to Sophie de Brandt in Berlin. He returned to build a house for her and the Adam brothers built a mansion of pink sandstone. She never came as King Frederick of Prussia forbade it. Sophie never married.
Finally going east you cross the border for the last time and roll towards Berwick upon Tweed. Before you get there you have to cross the A1. A traffic island in the middle makes it easier but cars still race by at over 70mph so allow plenty of time. Between the A1 and Berwick there's a short section of cycle path, then you're on roads, you pass the train station as you enter the town. There's a bike shop.