The extra letters from wordplay spelt out “illuminated manuscript” and “versal in largest cell”. Accordingly, the top-left cell had to be 3×3, containing a large (somewhat ornate) A that was shared by multiple across and down entries. The highlighted title was Book of Kells, an illuminated manuscript of the New Testament gospels. The puzzle’s title hinted at “non-U litmus” = LITMS, ie LIT (illuminated) MS (manuscript).
Conventions: * = anagram, < = reversal
| Answer | Explanation [extra letter] |
|---|---|
| AUREUS | (T)A(c)[I](t)U(s) + SURE * |
| APERÇU | AP + CRUE[L] * |
| HERB | (H + B(abe)) around ([L]E + R) |
| RUBATOS | RUB + A[U]TOS |
| BREED | [M]B + RED around E(pidemic) |
| OF NOTE | [I]O + NOT in FE |
| UPTREND | PUT * + [N]R + END |
| KEEN | [A]E in KEN |
| LEPPED | PEL[T] < + PED |
| OBELI | (pr)OB[E] ELI(minated) |
| REFOOT | ROOT around [D]EF |
| ATTACKER | [M]ATER around TACK |
| NAVE | [A]NA + ’VE |
| SCELERATE | (TEE[N]S CLEAR) * |
| JELL | EL[U]L around J(une) |
| FÊTE | FE[S]T + E |
| GALA | G[C]A + L(ook) A(ctive) |
| ENGENDER | [R]END in GREEN * |
| PSALTERY | (S[I]GHT-PLAYER − (G + H(armony))) * |
| BEDE | D in BEE[P] |
| ABULIA | BUIL[T] * in AA |
| ARPENT | P in TA[V]ERN * |
| UPPER | (cantalo)UP[E] PER(haps) |
| RED DEER | ’RE + O[R]DERED * − O |
| ERRAND | ARR < in [S]END |
| SUBFLOOR | (OF L[A]BOUR’S) * |
| SHANKBONE | SHONE around ([L]ANK + (ri)B) |
| VETO | V[I]E + TO |
| TROT | [N]OT after T(eacher’s) R(outine) |
| IBSENITE | (TEEN IS) * after [L]IB |
| DEFEAT | MEAT with DE[A]F for the first letter |
| ELEVATED | E + T[R]AVELLED * − L |
| PATELLA | LA[G] after PLATE * |
| FALLAL | FALL around L[E]A |
| KRONE | (NOR[S]E + K) * |
| CEAS | C(reating) E(mpty) [T](houghts) A(round) S(tage) |
| EVET | EVI[C]T with E for I |
| THEY | TH(ieves) + EY[E] |
| CEDE | CE[L] + ED < |
| MERE | RE[L] after ME |