Hispano Aviacion P.300
Exactly Brian!
"The same German-Spanish team that also designed the HA-100, designed later a light-weight supersonic interceptor with delta shaped wings designated as HA-300. For aerodynamic testing, a manned glider version was built by Hispano as the HA.P-300. However, the first flight was aborted soon after lift off behind a CASA HE-111 towing plane because the plane showed to be highly unstable. No further attempts were made to fly it further.
Over to you
HP why didn't you ask if it was a glider
