D1 contracted D2 (supposedly competent) to remove a tree from his garden but D2 did the work so badly that a branch caused telephone wires to fall across the wires ontop a highway. P, a neighbour, went to pick up the wires and was struck by D3 who came round the bend and was driving too quickly. P sued all 3. D2 was liable, and CA held that D3 was indeed liable, but D1 was not.
Widgery LJ: generally an employer (E) is not vicariously liable for the acts of an independent contractor (only the employer’s own servants). There are exceptional cases where the employer can be liable for independent contractor’s (IC) negligence where E owes the victim a duty of care directly. He says that a class of case where E can be laible for IC is “extra hazardous” acts i.e. where the acts commissioned are so hazardous in their nature that it is proper to impose a direct obligation on E to see that proper care is taken. This does not apply here since the act could have been carried out without danger to anyone if the IC had been competent.