The free plant will be Penstemon ‘Drinkstone Red’. It’s described as:
A good red, hardy Penstemon, flowers for a long period over the summer with long tubular flowers and medium green foliage with an elegant appearance. It should be kept deadheaded to encourage flowering and cut back in spring to new shoots coming from the base.
This cultivar was bred by Fred Barcock at his Drinkstone Nursery in Suffolk. It is currently available from 4 supplier in the RHS Plantfinder.
The material for the free plant came from The Suffolk Punch Garden at Hollesley, where there is a National Plant Collection of plants introduced or bred in Suffolk.