Rubbing a wet leaf between my fingers produced a slight soapy feel confirming that this is soapwort.  The leaves and stems of soapwort used to be boiled in water to produce a soapy green lather which was used for washing.  Wild Soapwort (Saponaria officinalis) is fairly rare in Scotland and more commonly found in areas near old woollen mills where it was cultivated for cleaning wool and until very recently it was also used for cleaning delicate fabrics and tapestries.  It is sometimes seen in gardens now where the pink flowers give off a perfume in the evening which attracts moths.   This is most probably wild as there are no houses anywhere nearby but perhaps it was grown for cleaning the monks’ vestments at the former abbey which was close by.