William Edward Frost R.A. (1810-1877) - Classical scene with knights and maidens

A fascinating composition of a mystical scene with knights and maidens present. Although (as yet) an unidentified scene, it clearly depicts a classical story and is likely from  a classical literature source. Frost would often use historical, classical or mythological sources for his paintings and this is superb example. The use of knights in armour suggests it is from the crusades or the medieval period in general. The fact that Frost has used RA in the signature furthermore points to this work being painted after his election in 1870. This work may be a study for a larger composition or exhibition piece. Further research and restoration would certainly help the watercolour.
 
Medium: watercolour and on paper, signed l.r. 'W E Frost RA' 24.2 x 33.4cm (arched top), mounted. 
 
Provenance: Albany Gallery (stock number: 8500); Private collection, UK.
 
Condition report: various foxing marks and time staining. There is a small tear in the bottom left-hand corner. Please see photographs. The condition is reflected in the lower price. The mount is also slighly bumped in the bottom right-hand corner.