In Emmett v Sisson  the Court of Appeal was asked to consider both the extent of a right of way and whether there had been actionable interference with it.
The right of way was an easement over land - a right which benefits property over the land of another person. Interference with an easement gives rise to an action for private nuisance but, in order to succeed, the person claiming nuisance must show:
- that it is entitled to the benefit of the easement
- the nature, extent and scope of the easement
- that the interference with the easement is substantial, a trivial impact on the use of an easement is not sufficient to succeed in an action for interference
In Emmett v Sisson, the parties owned two neighbouring properties. The land belonging to Mr and Mrs Sisson had the benefit of 'a right of way... with or without vehicles and for all reasonable purposes in connection with the proper use of the Property over and along the access way'.
The access way referred to was a driveway. Sisson erected a low stone wall along the entire length of the driveway with a gate at the far end. The wall was low enough to step over.
Some years later, Mr and Mrs Emmett, who owned the driveway and an adjacent property constructed foundation for a 2 metre high wall along the boundary of the driveway just a few centimetres from the low wall. The Sissons removed the low wall and issued proceedings seeking an injunction to prevent the high wall being built, claiming that its construction interfered with their right of way.
The Court of Appeal had to decide:
- whether the Sissons had a right to gain access to their land along the whole length of the right of way, or only at certain points
- if so, would the erection of a wall along the length of the right of way, with one suitable vehicular entrance to Sisson's property, constitute an actionable interference to their right of way?
The court considered the wording of the right of way. It concluded that whilst this may limit the purpose for which the grant of the right was made it did not limit the physical extent of the easement. The words granted a linear access along the whole of the boundary with the driveway. There was nothing in the drafting which limited the access to the property to any one point or a number of points.
This construction was supported by a provision elsewhere in the conveyance which required the Sissons to fence around their land on all sides excepting the boundary which ran along the right of way. This implied a right to have free access to their land along the whole length of it.
Having disposed of the issue of constructing the right of way, the court reviewed case law relating to actionable interference with easements. This was summed up in B&Q PLC v Liverpool and Lancashire Properties Ltd  as follows:
'In short, the test is one of convenience and not necessity or reasonable necessity. Provided that what the grantee is insisting on is not unreasonable, the question is: can the right of way be substantially and practically exercised as conveniently as before?'
The court acknowledged that the right of way granted to the Sissons might be a 'relative luxury' - in so far as it allowed vehicular and pedestrian access along a 30 metres stretch - but that is what the conveyance gave them as their right. It was not unreasonable for the Sissons to insist on exercising the whole of the right that was granted to them.
In conclusion, the construction of the wall would amount to a severe restriction on the vehicular and pedestrian access to Sissons' property as they would not be able to exercise the right of way in the manner envisaged by the conveyance.