Across:
1. America's first saint in chamber signs in regularly (7)
5. Task fan performed in robes (7)
9. Really first Russian region of the country (5)
10. Declare dissolved nitrogen to be involved in broken ulna (5)
11. Big potential difference could result in this with American pope's type? (3)
12. Plant flagpole and erect housing (8)
13. To the west, those finishing the teenager phase relish group debutantes' ball (6)
15. Hero's identification with cold heart (4)
16. Overlooked, Spurs vied desperately around Europe (10)
19. Programming language launches, with jury (users) initially out... these things can go downhill awfully fast (10)
20. see 19 down
23. He ruled 29 and administered by force, firm (6)
25. Liberally wire funds, allowing second last of children to go and have some fun on the drink (8)
27. Intention to return - without taking long - to get the rest (3)
28. Matter fiasco, until contained (5)
29. Start of serious suffering for country (5)
30. Town near Cleveland named for Alsatian from old German capital (7)
31. He may be called into action on rough vessel sinking into British river (7)
Down:
1. see 26
2. Cranky person turned up strangely alone in part of 29 (for now?) (9)
3. Leaders of industry need leading... and away from the drink! (6)
4. Doctor! Quince a day failing to measure up! (10)
5. Powerful person appropriating without thanks (4)
6. Drive pile further back to accommodate 5 of 29, son of 21 (6 2)
7. Saw the last two and a bit millennia? (5)
8. Finally Rex, turning 100, excused to run off and prosper (7)
14. Setter on MDMA had seizure, and ended up better off (10)
17. Going into long spell, knocked back aluminium sulfate or perhaps caffeine (9)
18. Laughable fail with crack scheme to take out 5 (8)
19,20ac. Last 5 of 29 before 23's rule anxious if oil processed but not uranium (7 4)
21. He was 28 of 2 and son of 19, as 29 fan tends to maintain (7)
22. Passed over, return having conquered European city (6)
24. Company fined heavily in Europe start to put in desperate plea (5)
26,1dn. Jocular (as in quite silly) 5 who 16 transition in 29 after 23 (4 6 1)
Solution:
CABRINI=KAFTANS|
A=A=N=N=I=E=D=U|
RURAL=ANNUL=ARC|
L=C=A=D=G=I=G=C|
OLEANDER=SPHERE|
S=L=D=Q=B=E===E|
IDOL=SUPERVISED|
==N=F=A=N=I=T==|
AVALANCHES=XIII|
L===R=Y=F=O=M=N|
FRANCO=WINDSURF|
O=P=I=J=T=E=L=A|
NAP=COUNT=SPAIN|
S=L=A=A=E=S=N=T|
OBERLIN=DRAFTEE|
Name: 877 - Jocular Rule
Author: by BenDR

Annos-Across:
1. alt (ChAmBeR sIgNs In)
5. *(TASK FAN)
9. R + URAL
10. N in *ULNA
11. A + RC
12. tel (flagp)OLE AND ER(ect)
13. rev tails acrostic
15. ID + (c)OL(d)
16. E in *(SPURS VIED)
19. (j)AVA LA(u)NCHES
23. F + RAN + CO
25. *(WIRE FUNDS) - E
27. r(P(l)AN)
28. tel (fias)CO UNT(il)
29. S(erious) + PAIN
30. O + BERLIN
31. D(RAFT)EE
Annos-Down:
2. r(CRAB) + *ALONE
3. I N L + AND
4. *(QUINCE A DAY)
5. (ta)KING
6. rev tel (dr)IVE PILE F(urther) <
7. AD + AGE
8. *EXCUSED with X -> C
14. BEN + E + FITTED
17. rev( ALUM ) in STINT
18. *(FAIL CRACK) - K
19,20ac. *(ANXIOUS IF OIL) - U
21. tel (Spa)IN FAN TE(nds)
22. rev tel (p)ASSED O(ver) <
24. P in *PLEA
26,1dn. *(JOCULAR AS IN)
Defs-Across:
1. America's first saint
5. robes
9. of the country
10. Declare dissolved
11. Big potential difference could result in this
12. Plant
13. ball
15. Hero
16. Overlooked
19. these things can go downhill awfully fast
23. He ruled 29
25. have some fun on the drink
27. the rest
28. Matter
29. country
30. Town near Cleveland named for Alsatian
31. He may be called into action
Defs-Down:
2. part of 29 (for now?)
3. away from the drink!
4. failing to measure up
5. Powerful person
6. 5 of 29, son of 21
7. Saw
8. prosper
14. ended up better off
17. perhaps caffeine
18. Laughable
19,20ac. Last 5 of 29 before 23's rule
21. He was 28 of 2 and son of 19
22. European city
24. Company fined heavily in Europe
26,1dn. 5 who 16 transition in 29 after 23