READING FC crashed to their heaviest defeat of the Championship season after a second-half horror show at the Hawthorns.

Royals hadn’t lost a game by more than one goal this season until they were blown apart by West Brom in a nightmare 45-minute spell.

Paul Clement’s men deservedly led 1-0 at the break through Leandro Bacuna’s stunning sixth-minute strike.

But they capitulated after the interval as a Dwight Gayle brace followed by Harvey Barnes and Kyle Bartley goals sent the hosts up to second in the table.

This was the proverbial game of two halves, with Clement’s men looking every bit a well-drilled outfit and a serious threat in front goal.

But after the break they appeared bereft of confidence and more like a side destined for another relegation battle.

To compound their misery, goalkeeper Sam Walker could have done better for Gayle’s goals on 49 and 65 minutes before Barnes on 72 and Bartley on 80 completed the rout.

Clement’s men now head into a fortnight’s international break on the back of a hiding and with pressure mounting on the Reading boss, with only goal difference keeping his side out of the relegation zone.

Clement made three changes to the side that lost at home to QPR on Tuesday night.

With top-scorer Jon Dadi Bodvarsson and Sam Baldock both missing through injury, Marc McNulty started up front. John Swift and Tyler Blackett also came in and 18-year-old Academy defender Tom Holmes was named on the bench.

That meant there was no place for Sone Aluko, Mo Barrow and Liam Kelly in a 5-3-2 formation aimed at frustrating Darren Moore's hosts.

Baggies went close in the first minute when Jay Rodriguez headed wide from a Jake Livermore cross.

But Royals quickly ruined Baggies’ early optimism by taking a shock sixth-minute lead.

Saeid Ezatolahi earned a corner when his 25-yard piledriver was pushed out by West Brom keeper Sam Johnstone.

The hosts then switched off as Swift knocked Bacuna’s short corner back into his path, and the ex-Aston Villa midfielder struck a delicious shot past Johnstone and in off the far post.

Reading looked to build on the lead and saw Ezatolahi fire over from a Swift assist. Then Johnstone held on to a Yakou Meite header from the centre of the box after more good work by Bacuna.

It had been a sluggish start by Moore’s men, but they soon stepped it up and almost levelled on 19 minutes. Blackett and Meite messed up in midfield and Harvey Barnes pounced, only for his shot to clip the outside of Walker’s far post.

Reading, though, hit back as Bacuna’s pass split the Baggies defence open only for McNulty to drag his effort wide when he should have hit the target.

Barnes went close again at the other end with a long-range drive, but Royals threatened a second on 27 minutes. Bacuna was the architect with a delightful cross, but Meite got his header wrong when he should have done better and Blackett failed to hit the target from the subsequent loose ball.

Back came West Brom with Craig Dawson nodding wide from a corner, then Gayle fired past Walker only for the alert Liam Moore to clear the ball off the line.

Royals even managed to snuff out any further danger before the break and went in with a deserved lead.

Yet the visitors were pegged back by Baggies less than four minutes into the second half.

Walker completely misjudged a looping corner from Tyrone Mears and Gayle was lurking at the back post to head in from a tight angle.

Royals were coming under more and more pressure – yet they could have gone back in front in the 65th minute when Swift’s first-time shot from a Chris Gunter cross forced a decent save out of Johnstone.

It was the turning point of the match as the home side went straight up the other end and scored less than a minute later.

Again, Walker didn’t cover himself in glory as Kyle Bartley’s header from a Barnes corner bounced up over the keeper’s head before Gayle got the final touch from close range.

It was a massive blow for the Royals and Clement was about to make a double substitution when West Brom grabbed their third to kill off the match.

This time they sliced through the Reading midfield like a knife through butter before Barnes collected the final pass and slotted past Walker with ease.

That was game over – but there was more pain to come as the Baggies added a fourth 10 minutes before the end.

There was nothing complicated about it, the unmarked Bartley rising highest to meet a Chris Brunt corner with a header from 15 yards that flew past Walker.

Royals were never coming back from that and only a fine save from Walker to deny Rodriguez prevented a West Brom fifth in the closing stages.

Clement now has two weeks to work out how to reverse his side’s woeful form before they host Millwall – the side immediately above them in the table – on October 20.

West Brom: Johnstone, Gibbs, Bartley, Livermore (Brunt 67), Mears (Edwards 62), Barnes (Adarabioyo 88), Gayle, Barry (c), Rodriguez, Dawson, Hegazi. Subs not used: Myhill, Robson-Kanu, Townsend, Hoolahan. Booked: Dawson 41, Barry 52.

Reading: Walker, Gunter (Sims 77), Ilori, Blackett, Moore, Yiadom, Ezatolahi, Bacuna (Kelly 81), Swift, McNulty (Barrow 77), Meite. Subs not used: Aluko, Mannone, Holmes, Rinomhota. Booked: Swift 51, Ilori 56, Moore 82.

Referee: Darren England.

Attendance: 22,865 (Reading 907).