This is an interesting, and obviously rare little vessel. With a stepped hull construction, this little baby will undoubtedly fly!

A stepped hull's purpose is to ventilate the bottom of the hull to reduce the friction, causing the vessel to hydroplane across the surface of the water. The combination of lift and the reduced friction with the stepped hull helps the boat go faster.  These racers are often built as lightly as possible; lesser the weight, faster the ride concept. But negatively, they tended not to last for great lengths of time, which is what makes the originality of this little boat quite unique.

After much research the owner found that this boat was commissioned by a wealthy sportsman who had a large collection of antique boats. Amidst his collections of Ditchburns, Minnets, Hunters and Greavettes, he had 4 racing boats. Allez IV was the last one of the race boats that he had commissioned by Tom Greavette, using a Bert Hawker design. 
Notable also, is the motor used on Allez IV. Its unique twin horizontal rotary valve fuel induction system was designed by Lockwood Motor Co in 1929. There were only 40 of these models - A Speedibee - built, and only five remain as far as we know of.