On the second page of In Parenthesis, the following passage occurs:
From where he stood heavily, irksomely at ease, he could see, half-left between 7 and 8 of the front rank, the profile of Jenkins and the elegant cut of his war-time rig and his flax head held front; like San Romano’s foreground squire, unhelmeted; but we don’t have lances now nor banners nor trumpets. It pains the lips to think of bugles—and did they blow Defaulters on the Uccello horns.
When I first read this, many years ago, it must have been quite frustrating. Sure, there’s a footnote to tell me “San Romano” refers to “painting, ‘Rout of San Romano’. Paolo Uccello (Nat. Gal.),” but not being in London, I couldn’t trot down to the National Gallery to have a look. Of course I could have scoured the art section of the library for a reproduction, but you can’t really go to that kind of trouble for every passing reference. The OED would have told me that defaulter (in military use) is “A soldier guilty of a military crime or offence,” but that doesn’t go very far in explaining the reference. Now, with the wonders of the internet, I can google “San Romano, Uccello” and find any number of reproductions—this page provides a nice large image, if somewhat dark, while this one is considerably brighter—as well as the start of an article explaining who the “foreground squire” is (the Florentine Captain-General, Niccolo Mauruzzi da Tolentino, who, Wikipedia informs us, was in his 80s when he led his troops at the Battle of San Romano in April of 1432!).
As for Defaulters, this page tells us that the tune was probably “A Man’s A Man For A’ That,” which
is traditionally played when an accused soldier is brought before a summary trial, court martial or other hearing. By tradition, the accused removes his hat and is escorted in by two soldiers of equal rank – his peers – and is permitted to have a piper play him in. The tune is played to bring to mind Burns’ words – and remind the presiding officer that the soldier is still a man, and should be treated fairly and without prejudice no matter what the accusation against him might be. The tune is played by a solo piper.
And this page has a link to a midi file of the tune (not to mention Reveille, Dinner Call, Lights Out, and Lament). So a few seconds with Google gave me a basic understanding of the realia Jones had in mind when composing the passage; without Google, I have no idea how long it would have taken me to amass the knowledge, but it wouldn’t have been worth the effort involved. All hail the internet!