THE roof was open, the rain hammered down, the ball was greasy, but Wales were never going to let a Grand Slam slip from their grasp.

From the moment Gareth Anscombe kicked off at Principality Stadium, Warren Gatland’s men were on the money against Ireland to make it a remarkably comfortable Six Nations coronation rather than the expected tense one.

It took just 70 seconds for Hadleigh Parkes to cross after the start of dreams and Wales never looked back when securing their first Six Nations clean sweep since 2012.

South Wales Argus: OPENER: Hadleigh Parkes charges overOPENER: Hadleigh Parkes charges over

They got their noses in front and the conditions meant it wasn’t an afternoon for chasing; the Irish coaching team must have looked to the skies and lamented their decision not to shut the roof.

Wales headed into the clash with a steely determination to finish the job and this was their most convincing win, a record-breaking 14th Test success on the spin in which Anscombe booted 20 points without missing.

After needing a rousing comeback in Paris, getting the job done unconvincingly in Rome, storming back in the final quarter to beat England and surviving a scare in Edinburgh, this was comfortably their best performance.

They kept errors to a minimum when the weather could have made them frequent. They kept their cool while the Irish were tetchy. They kept the scoreboard ticking and defended with accuracy and discipline to ensure Ireland only moved off nil when the clock hit red.

Remarkably, they hammered the champions and still probably feel they had a few more gears to go through.

The Irish headed to Cardiff with slim hopes of retaining their title but there was to be no party-pooping on a day that hammered home how much Gatland will be missed.

South Wales Argus:

Under his stewardship Wales have had the habit of winning when it really matters against European rivals.

Now, after making history by becoming the first coach to win a hat-trick of Grand Slams, the New Zealander will start plotting another happy finale in the big one at the World Cup.

Gatland spoke about going under the radar last autumn but there is no chance of that now.

Wales were on it from the off –Anscombe’s kick-off chased hard by George North to bundle Jacob Stockdale into touch in the 22.

A lineout drive, charge by hooker Ken Owens and chip by Anscombe led to a Parkes try with 70 seconds on the clock.

The fly-half’s conversion made it a 7-0 lead but it took a wonderful cover tackle in the 22 by the try hero to keep the advantage after a cunning cross-field kick from a penalty set Stockdale racing down the left.

South Wales Argus:

But Wales’ pre-match plan was given a blow when wing North was forced off, leading to Dan Biggar’s ninth-minute introduction and a reshuffle with Anscombe moving to full-back and Liam Williams shifting to the wing.

The back-three change didn’t affect the forwards, however, and they laid siege to the Irish line with 17 phases only for Tadhg Beirne, the Munster lock who made his name with his breakdown prowess at the Scarlets, to pilfer the ball five metres out.

But Wales were soon 10 points to the good with a booming Anscombe penalty in the 18th minute, the Cardiff Blues playmaker punishing an Irish breakdown offence.

The chance to stretch further clear was lost by daft play by scrum-half Gareth Davies – who slammed into Bundee Aki on the floor when Wales were playing with penalty advantage – and the frustration was compounded when Ireland had their first bout of real pressure.

It took superb defence by lock Adam Beard and flanker Justin Tipuric to deny the visitors from a five-metre lineout and then the Irish wasted prime attacking position in front of the posts when CJ Stander knocked on from a quick tap.

Wales were winning the key moments and playing the horrid conditions – which were of Ireland’s making because of the roof – more smartly.

It became a 13-point lead in the 36th minute when Anscomble slotted a penalty after Ireland jumped the gun to be offside in midfield.

Wales needed to avoid giving the Irish a lifeline before the break, but instead they ended the half hunting a key score to make it a three-score game.

It came when the visitors were pinged at a scrum to allow Anscombe to make it 16-0.

At Murrayfield Wales failed to back up their first-half toil yet they were the first to strike after the resumption against an increasingly rattled Ireland; another breakdown offence allowed Anscombe to stretch the buffer to 19-0 after 48 minutes.

When Johnny Sexton, world player of the year, kicked the following restart dead it merely added to Welsh glee and Wales kept twisting the knife.

Anscombe’s boot made it 22-0 as the hour approached and only the biggest of implosions would deny a Grand Slam.

Instead it was almost an anti-climax as Wales counted down to the popping of corks, with Anscombe adding to his tally with another three-pointer from the tee after 69 minutes.

That Wales had the job done yet still defended with tenacity to protect their line at the death – Ireland just sneaked over through replacement back Jordan Larmour – spoke volumes.

It was another Gatland Grand Slam constructed by Shaun Edwards and his fellow assistants Rob Howley, Robin McBryde and Neil Jenkins. They got their perfect send-off.

Wales: L Williams, G North (D Biggar 8), J Davies, H Parkes (O Watkin 70), J Adams, J Adams, G Anscombe, G Davies (A Davies 56), R Evans (N Smith 54), K Owens (E Dee 60), T Francis (D Lewis 54), A Beard (J Ball 70), AW Jones, J Navidi, J Tipuric, R Moriarty (A Wainwright 70).

Scorers: try – H Parkes; conversion – G Anscombe; penalties – G Anscombe (6)

Ireland: R Kearney (J Larmour 64), K Earls, G Ringrose, B Aki, J Stockdale, J Sexton (J Carty 72), C Murray (K Marmion 69), C Healy (D Kilcoyne 58), R Best (N Scannell 64), T Furlong (A Porter 64), T Beirne (Q Roux 58), J Ryan, P O’Mahony, S O’Brien (J Conan 49), CJ Stander.

Scorers: try – J Larmour; conversion – J Carty

Referee: Angus Gardner (New Zealand)