Ok, now i'm sure! I have seen this prototype few years ago at Museo Storico Dell' Aeronautica Militare - Vigna di Valle-
(from Wikipedia)
The Aerfer Ariete (Italian for Ram) was a prototype fighter aircraft built in Italy in 1958. It was a refined derivative of the Aerfer Sagittario 2, and was an attempt to bring that aircraft up to a standard where it could be mass-produced as a viable combat aircraft.
Retaining most of the Sagittario 2's layout with a nose intake and ventral exhaust for the main Derwent engine, the Ariete added a Rolls-Royce Soar RS.2 auxiliary turbojet engine to provide additional power for climbing and sprinting. This used a dorsal, retractable intake with its exhaust at the tail.
No production ensued; a proposed version with an auxiliary rocket engine instead of the auxiliary turbojet, the Aerfer Leone, was abandoned before a prototype could be built.
Ciao!
Titus