Torque is a measure of the engine's turning force at the crankshaft. BHP is a measure of the engine's power, that is the rate that work is done.
An engine's output BHP depends on the torque and the engine speed (RPM)
At a given engine speed, say 2000RPM, an engine with a high torque will produce more power than an engine with a smaller torque.
Diesel engines typically produce a high torque at low RPMs so are more powerful than their petrol equivalents at the same engine speed.
Petrol engines can rev higher than diesel engines so can produce high BHPs even though their torque may be low.
A petrol or diesel engine does not produce maximum torque at maximum RPM