Soul was chosen after a pitch against the incumbent agency, Cogent, and Miles Calcraft Briginshaw Duffy.
The review is part of NFU Mutual's plans to broaden its market to include well-off people with second homes in the country as well as those with a general interest in the countryside.
Founded 90 years ago as part of the National Farmers Union, NFU Mutual has declared that it will not follow the lead of other mutuals, including major building societies and insurers, by transforming itself into a public company.
Its stance is reflected in a requirement on all policy holders that they should donate any "windfall" profits to an NFU charity if demutualisation should take place.
Soul's brief will be to build NFU Mutual's credentials beyond the agricultural market, where it is almost universally known, to a wider world where few have heard of it.
Meanwhile, Soul has extended its relationship with Ken Livingstone's Greater London Authority with its appointment to run a campaign publicising the arrival of 1,500 more police officers on London's streets.
The campaign will emphasise the wide ethnic backgrounds of the officers.
It will also include six-sheet posters in crime hotspots telling criminals and the public exactly how many extra officers have been drafted into that area.
Kevin Brown, a partner at Soul, said: "We have taken a great deal of care to ensure the posters are situated geographically where they can provide the most reassurance for the public."