Internal Transport Barriers (ITB) in JET exhibit some remarkable features regarding their relation toward the shearing rate and the current profile. A database has been collected over a large number of pulses, and focuses on some specific plasma parameters at the barrier location : the gradient lengths, safety factor (q), magnetic shear (s), and shearing rate (γE). In the present work, we analyse the database in two different perspectives. First, we address the question of the shearing rate and its two contributions, i.e. toroidal rotation and diamagnetic term : we find that the plasma toroidal rotation is the dominant term, the diamagnetic contribution being estimated from the neoclassical drive. A correlation between the velocity shear rate and the magnetic shear is found, in agreement with previous works, and a minimum is seen at low magnetic shear. The definition of ITB as a departure from profile stiffness is compared to the use of the JET ITB criterion, and both approaches are found to be consistent. Second, we address the question of the barrier localisation in relation to the safety factor and the magnetic shear. We find that barriers are sensitive to rational q surfaces, as far as their location and performance are concerned. In reversed shear plasmas, obtained by applying current drive during the plasma ramp up, ITB can also be sustained in the negative shear region, where integer values of the safety factor does not seem to play a role.