Doublets by Auctor

Half of the across and half of the down clues are "double definitions" leading to two words that differ by one letter. Solvers should deduce which to enter and which letter to retain to form a two-word phrase. The remaining clues are normal. Solvers should highlight a relevant name. Chambers 98 is recommended, Collins justifies three proper names.

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Across
1 Somehow force a rethink finally, on energy. I do! (8)
10 Mason's bench supporter (6)
11 Noisy inclined to shudder (5)
13 Skirting Mafia, policeman's lead included heroin dropped from stash (8)
14 Repeat article with ending changed for class (7)
15 Pen a literary composition as of old (5)
16 Suddenly poetic hush after a trick (6)
19 Put on trial Thera's little relative? (4)
20 My child in Dublin, one almost to secure a First in Humanities after lesson's end… (7)
21 … considers semester nearly done (7)
24 A person opposed to white wine (4)
27 After disciple's accepted New Testament is voiced (6)
28 Twisted addict (5)
29 Sofas in theatre box seating one local society (7)
30 Essentially a resort? Aye, S. ____ could be (8)
32 Dutch city, one to maintain original doctrine (5)
33 Force a way into a state capital (6)
34 More off-white - more lovely (8)
Down
1 After head's demoted, argument about religious studies is lit up (8)
2 Taxi expert (3)
3 Storms free leaves (6)
4 Commentator's take on European memorial tablet in US (8)
5 Ask for the umpire's decision to be published (6)
6 Whatsit's snitch cut short by one such as Mary P (10)
7 Wax marker coloured fabric (6)
8 Ply makes fallen trunks spin (5)
9 Give up an old prayer (4)
12 Associate with mendicant senior, disturbed when nothing's left (10)
17 Return of Son of God is a U about love first - below average (8)
18 Rest with new clothes-whitener? (8)
22 Tangled tuft bields tavers o' unknotted tie (6)
23 Grain grinder? (6)
25 In Indian a garish script (6)
26 Nonsense, sweetheart! (5)
28 Hasten mistiness (4)
31 Chilling software for protecting privacy (3)

To enter the July 2001 Prize Competition send the 2-word phrase and a normal cryptic clue to  the 8-letter name. Send to me at derek@crossword.org.uk The writer of the best clue will win a copy of Chambers Book of Facts which has been donated by Chambers/Harrap. The competition will close at midnight BST on 31 July.
Please feel free to send your comments on this puzzle to "auctor@auctor.co.uk"