ACROSS
1 The ultimate destination of northern tax collectors taking truck to Austria (7)
5 See 26
9,15 Account of 11 tells trite heist falsely (3,6,6)
10 At first transfix His Eminence with number one topic (5)
11 Stimulate mother, unhappy reportedly with PI (6,7)
13 See 16
15 See 9
17 The French captured retreating dog with hoists (3-3)
19 Megan lap danced. It's the manager's idea! (4,4)
22 Knock out person (clang!) on the carpet (5,8)
25 Superior adult books books! (5)
26,5A Detain healthy elk! Order features 11 (3,4,2,3,4)
27,18 11's extended valediction (3,4,7)
28 Presumably elephants never eat them (7)

DOWN
1 Heartless nudist is bats. Bats! (4)
2 Again force out northbound leper carrying letter (2-5)
3 Errant bailiff appears for the defence, but not very loudly! (5)
4 Remarkably, hall isn't providing homes for insects (3-5)
5 The Right writing with some heat (6)
6 Outrageously restive ox is demanding with violence (9)
7 Locates extraordinary costmary plant (7)
8 Regard main arena as too hot to watch (3-7)
12 Old sponger who could perceive the banquet? (5-5)
14 In Virginia river otter swims around the water bus (9)
16,13 11 narration of way every moll fell drunkenly (8,2,6)
18 See 27
20 Extras amount to fifty English gigabytes? Positively! (3,4)
21 Rover's identity in tail! Tail? (3,3)
23 It's unsuitable to be not out with westbound Father Time (5)
24 Responsibility for sailor grasping Greek character (4)