I don’t get to blog Magwitch very often which is a shame as I really enjoyed this puzzle.  Thanks Magwitch.
After solving 1 down and 1 across I was expecting a theme of industrial unrest, though in the end it never happened.

| Across | ||
| 1 | TARGET | Strike breaker goes back to achieve objective (6) | 
| RAT (strike breaker) reversed (goes back) and GET (to achieve) | ||
| 4 | CALAMITY | A strike in the heart of London causes disaster (8) | 
| A LAM (strike) in CITY (heart of London) – the City of London (or just the City) is the name for the original historical city at the centre of the greater London metropolis, now almost exclusively a financial centre and business district. | ||
| 9 | ROLL-UP | Europe centrally has influence over high risk betting system (4,2) | 
| euROpe (centre of) and PULL (influence) reversed (over) | ||
| 10 | MERCIFUL | Forgiving about foul crime after nothing is lost (8) | 
| anagram (about, moving around) of FoUL CRIME missing O (nothing) | ||
| 12 | INACTIVE | During performance I have to be quiet (8) | 
| IN (during) ACT (performance) and I’VE (I have) | ||
| 13 | SPARSE | Rare for solver initially to work out breakdown of clue (6) | 
| Solver (initail letter of) and PARSE (to work out breakdown of clue) – I remeber some discussions on this site whether ‘parse’ could be used to describe the activity of explaining a clue or not. I couldn’t see the problem myself. | ||
| 15 | UGLY | Nasty judge regularly gets extremely lonely (4) | 
| jUdGe (regular selection from) and LonelY (extreme letters of) | ||
| 16 | TRIPPER | Slip through as a visitor (7) | 
| TRIP (slip) and PER (through) | ||
| 20 | HAGGARD | Set including outrageous gag is wasted (7) | 
| GAG* anagram=outrageous inside HARD (set) | ||
| 21 | STUN | Shock arrest after model goes missing (4) | 
| STUNt (arrest) missing T (model T Ford) | ||
| 25 | REBUKE | Take to task about UK invading the outskirts of Belgrade (6) | 
| RE (regarding, about) tehn UK inside (invading) BelgradE (outskirts of) | ||
| 26 | STALWART | Loyal supporter resolved last conflict with Tory leader (8) | 
| LAST* anagram=resolved then WAR (conflict) and Tory (leading letter of) | ||
| 28 | TRIBUNAL | Panel of judges bother about the point retrospectively (8) | 
| TRIAL (bother) contains (about) NUB (the point) reversed (retrospectively) | ||
| 29 | MARGIN | Starts to mount armed resistance against soldier on northern border (6) | 
| Mount Armed Resistance (starting letters of) teh GI (soldier) and N (northern) | ||
| 30 | SPECTATE | Watch police state collapse after oil disappears (8) | 
| anagram (collapse) of PoliCE STATE missing OIL | ||
| 31 | STREET | Army corps goes in to restore highway (6) | 
| RE (royal Engineers, army corps) inside (goes in to) STET (restore, printing and proof-reading) | ||
| Down | ||
| 1 | TERMINUS | End of the road for miners involved with trade union (8) | 
| anagram (involved) of MINERS and TU (trade union) | ||
| 2 | RELIABLE | Trustworthy person who stops boat sinking after capsize on deserted lake (8) | 
| BAILER (person who stops boat sinking) reversed (after capsize) on LakE (deserted, empty, no middle letters) | ||
| 3 | EQUITY | Right for the old to be upset over surrender (6) | 
| YE (the, old) reversed (to be upset) containing (over) QUIT (surrender) | ||
| 5 | ANEW | Engaged in insane warfare again (4) | 
| found inside (engaged in) insANE Warfare | ||
| 6 | ACCEPTED | Usual to say yes to newspaper boss (8) | 
| ACCEPT (say yes to) and ED (editor, newspaper boss) | ||
| 7 | INFIRM | Failing business goes under at home (6) | 
| FIRM (business) under IN (at home) | ||
| 8 | YELLED | Unknown 50% misspelled “screamed” (6) | 
| Y (unknown, maths) then misspELLED (50% of the letters) | ||
| 11 | AVERAGE | Mean to declare how old you are (7) | 
| AVER AGE (to declare how old you are) | ||
| 14 | OPERATE | Post Office raised online price of work (7) | 
| PO (post office) reversed (raised) then E (online, e-commrce etc) and RATE (price of) | ||
| 17 | BANKRUPT | Broke embargo on Scandinavian currency over time (8) | 
| BAN (embargo) on KR (krone, Scandinavian currency) UP (over) T (time) | ||
| 18 | STRANGLE | Kill foreigner with the other hand finally pushed slightly forward (8) | 
| STRANGEr (foreigner) with L replacing R (with the other hand) and the last letter moved up one place (finally pushed slightly forward) | ||
| 19 | INSTINCT | Gut reaction isn’t out of place in court (8) | 
| anagram (out of place) of ISN’T then IN CT (court) | ||
| 22 | WRITES | Is a composer of liturgies we hear (6) | 
| sounds like (we hear) rites (liturgies) | ||
| 23 | OBLIGE | Make the first pair of obsolescent lichens germinate (6) | 
| the first pair of letters of OBsolescent LIchens GErminate | ||
| 24 | PLIANT | Easy to manage first person in position (6) | 
| I (first person) in PLANT (position) | ||
| 27 | PACT | Cop ultimately gets to do a deal (4) | 
| coP (ultimate letter of) with ACT (to do) | ||
*anagram 
definitions are underlined
Very accomplished, very enjoyable. Thanks S & B
Thanks both.
The crossword itself was good, but the grid is unsatisfactory, as it comprises four separate quadrants with only one way into each part. I believe that this form of grid is banned in some quarters.
I always enjoy Magwitch, and today was no exception (given such an accomplished level of brain-wrestling and surface, I felt 6dn ACCEPTED was lame). So … thanks, Magwitch, for setting it, and PeeDee for writing about it.
PS I do tend to agree with Bracoman about the grid
Thanks Magwitch and PeeDee
Was able to do this in a shortened lunch break during a busy day – so it was perfect.
Finished up in the NW corner with RELIABLE (which took a little while to see BAILER going up) and EQUITY (where I hadn’t helped myself by writing in EX as the first two letters earlier) as the last couple in.
Thanks Magwitch and PeeDee.
In my hurry to complete I – unsatisfactorily – entered DROPPED at 16ac (dropped a catch, dropped in?) so not proud of myself.
Otherwise, 23dn should really have said “pairs” shouldn’t it? Or am I being over prickly.
Still, an enjoyable solve so no real complaints.
Hi Hamish re 23dn – I did not notice at the time, but yes you are correct. There are three pairs to be taken.