Very little is known abouth this tunnel, even its name. It is short, approx 50 yards and passes beneath the old Newport to Pontypool road at Llantarnam. It is solidly built and of an impressive guage. Due to its very early construction by the GWR, it appears to have been constructed to allow 'broad guage' trains to run through it, but whether broad guage trains ever ran through it is not known. Some concrete sleepers remain after track was removed in the 1960's.