I tried solving this at my desk at work last Tuesday, but it ended up being a lot busier than I thought it would so I didn't get a good run at it at all, so no idea what my solving time was. About two hours from start to finish, but that's meaningless. Of course, I'd already solved 1ac after Sotira's comment last week. I hope your mother's recovered from the shock, Sarah!
| Across |
| 1 | Conservative fanatic who demonstrated his limited powers? (4) |
| CNUT - C(onservative) + NUT (fanatic). King of England 1016-1035, better known with the anglicised spelling Canute, who commanded the tide to stop coming in to prove he wasn't all-powerful. |
| 4 | A set of stories about old soldier and saint — one studies the atmosphere (10) |
| AEROLOGIST - A + LORE (set of stories) reversed + O(ld) + GI (soldier) + ST (saint). |
| 9 | Humiliated, having difficult time, taking external knock (7,3) |
| BROUGHT LOW - ROUGH (difficult) + T(ime), inside BLOW (knock). |
| 10 | I had left foot chopped off, becoming unemployed (4) |
| IDLE - I'D (I had) + LEFT with the FT removed. |
| 11 | Woman with famous brothers, this person is on space station (6) |
| MIRIAM - I AM (this person is) next to MIR (space station). Miriam was the elder sister of Moses and Aaron in the Bible. |
| 12 | Manage half of answer briefly in treatise (8) |
| TRANSACT - ANS (half of answer, or answer briefly, but surely not both!) inside TRACT (treatise). |
| 14 | Some other god about to become a monster (4) |
| OGRE - hidden reversed in other god. |
| 15 | Rich man faces agony losing gold, disposing of business? (10) |
| DIVESTMENT - DIVES (rich man) + T(or)MENT (agony without or for gold). |
| 17 | Sweet dancer crossing street at end of journey (10) |
| GOBSTOPPER - BOPPER (dancer) around ST(reet), after GO (journey). |
| 20 | Rage in bar (4) |
| RAIL - double definition. |
| 21 | Borders of Mexico, region tricky for this chieftain (8) |
GERONIMO - (Mexico, region)*. Apache leader (1829-1909). |
| 23 | One praising old / Scottish entertainer (6) |
| LAUDER - double definition, i.e. someone who lauds, and Sir Harry Lauder (1870-1950), music hall comedian and singer. |
| 24 | Priest gets wicked learner to come forward (4) |
| LEVI - EVIL (wicked), with the L for learner moved to the front. Biblical priest, third son of Jacob in the Book of Genesis. |
| 25 | Instrument of torture the opposite of what female cryptically suggests? (4,6) |
| IRON MAIDEN - "female" would cryptically suggest FE (iron) + MALE (man), as opposed to the answer. |
| 26 | Biscuit and the rest Biggles’s companion gets? (6,4) |
| GINGERSNAP - GINGER'S (Biggles's companion's) NAP (rest). Ginger Hebblethwaite is the pilot's companion in the books by W. E. Johns. |
| 27 | Machine hospital lost, keeping people waiting? (4) |
| LATE - LATHE (machine), minus the H for hospital. |
| Down |
| 2 | Residence for infirm macho men can be seen doing it (7,4) |
| NURSING HOME - wordplay in the answer, as "macho men" can be seen "nursing" HOME. |
| 3 | Weekday interrupted by terrible fire — fellows obscured by smoke? (9) |
| THURIFERS - THURS (weekday) around (fire)*. |
| 4 | Not one of the authentic journalists overcome by remorse? (7) |
| ASHAMED - A SHAM ED is not an authentic journalist. |
| 5 | What could that be? (8,7) |
| RELATIVE PRONOUN - cryptic definition. "That" is an example of one. |
| 6 | Vulgar idiot grabs maiden in church, it's said (3,4) |
| LOW MASS - LOW (vulgar) + ASS (idiot) around M(aiden). |
| 7 | God ultimately involved with rain? (5) |
| INDRA - (D, rain)*, the D coming from the last letter of "God", so doing double duty. Hindu god of war and the weather, so a neat clue. |
| 8 | Rubbish about to be received as special gift? (5) |
| TREAT - TAT (rubbish) around RE (about). |
| 13 | Prisoner given punishment encountered any number inside being locked up (11) |
| CONFINEMENT - CON (prisoner) + FINE (punishment) + MET (encountered) around N (any number). |
| 16 | Puma's lair not right for another sort of animal (9) |
| MARSUPIAL - (puma's lair)*. |
| 18 | This person in musical is a famous actor (7) |
| OLIVIER - I (this person) inside OLIVER (musical). |
| 19 | Pitch on old country fair offering pickled food (7) |
| ROLLMOP - ROLL (pitch) + MOP (old country fair). I wasn't familiar with this meaning of mop, but Chambers says it's another name for a hiring fair, which was a fair or market where servants could be engaged. |
| 21 | Sawn-off weapon prisoner used in camp (5) |
| GULAG - GU(n) ("sawn-off" weapon) + LAG (prisoner). |
| 22 | Bird rushed around valley avoiding a lake (5) |
| RAVEN - RAN (rushed) around VALE (valley), minus AL (a lake). |