Section 154(1) of the Highways Act 1980 (HiA 1980) provides that where a tree, hedge or shrub overhangs a highway so as to endanger or obstruct the passage of vehicles or pedestrians, the highway authority may serve notice on the owner or occupier of the land on which it is growing, requiring the tree to be lopped or cut to remove the cause of the danger, obstruction or interference. By virtue of HiA 1980, s 154(4), upon a failure to comply with a notice, the authority may carry out the work required and recover the expenses reasonably incurred. HiA 1980, s 154, is consistent with a number of more general provisions of the Act that are also relevant here. HiA 1980, s 41,