A Barracuda tail jet as a possible carrier-launch experiment

Why did Britain consider fitting a Fairey Barracuda with an additional jet engine in the tail?

It was probably a testbed for early carrier-takeoff ideas. A production aircraft would need a different airframe suited to the propulsion arrangement.

An additional tail jet could have let a Barracuda test ideas for carrier takeoff with early jet propulsion. The arrangement is interpreted as an experimental testbed, with uncertainty about the proposal itself. A production aircraft would need an airframe optimized for the propulsion arrangement. That makes a purpose-built successor more plausible than adopting the modified Barracuda for regular service.