With no towpath the tunnel is little seen by Londoners other than those on a boat. It disappears under the picturesque Café Laville on Edgware Road, before coming out at Cunningham Place a quarter of a kilometre later.
Engineers from the Trust used a boat to travel through the tunnel to assess any structural changes that have occurred, including checking for cracks and damage to brick work. Their observations will now be analysed, before it's decided if any major repairs are needed.
Work began on the tunnel in 1812, before completion in 1816. The earth excavated when the tunnel was first dug was used to level land just north of the canal, which became the site of Lord's cricket ground. The building of the canal had cut through what had been the outfield of the previous site for the ground.
Traditionally horses that pulled canal boats would leave the canal at the entrance to the tunnel and be led up over the hill by road before rejoining the towpath on the other side. The boats, meanwhile, would be ‘legged' though the tunnel, which involved people lying on the boats on their backs and using their feet on the roof of the tunnel to ‘walk' the boat through.
Chris Reynard, principal surveyor at the Trust, said: "Maida Hill Tunnel is a really fascinating underground route in the heart of London. Not too many people will get to see inside it, as there is no towpath inside the tunnel, so it can only be experienced by people travelling through it by boat. A trip into the tunnel is like stepping back in time. It's dark, quiet, a little bit eerie and much of the brick work dates back to when the tunnel was first constructed two centuries ago. The Regent's Canal is arguably more popular than ever before and our inspection is a good example of the type of work needed to keep it in top shape."