Despite putting out a seriously under-strength line-up, home coach Lynn Howells had expressed confidence that his shadow squad could carve out the success they needed to keep in touch at the top of the table.

But they could find no answer to the pace, power and know-how of the Neath-Swansea combine, superbly orchestrated by former All Blacks scrum-half Justin Marshall.

The home side were in the hunt at the midway mark - but after that it was a one-way affair as the Welsh team secured the bonus point.

Edinburgh had looked the hungrier outfit during the initial sparring session, but they did not look like turning pressure into precious quick rewards.

Veteran stand-off Duncan Hodge, who insists he can still figure in Scotland's World Cup plans, controlled matters in the first quarter with a variety of accurate positional kicks.

He was handed an opportunity to edge the Gunners in front in the seventh minute when they earned a penalty close to the halfway line.

The kick was advanced 10 metres because of backchat from Marshall, but Hodge's effort drifted past the right-hand post.

Ben Cairns then burst into the contest with a bullocking 50-metre run which took the capital troops deep into enemy territory.

The move was carried on by Argentinian Lucio Lopez-Fleming and they were awarded a penalty.

The anticipation of the home fans turned to frustration as they watched Ally Strokosch being penalised for holding on to the ball too long after a quick tap and dash by Cairns.

The reprieve spurred the Welsh side into mounting their first threatening raid of the game through a Marshall chip - but the move came to nothing.

It was an all-action end to the half. Edinburgh powered in front with a 25th-minute touchdown by utility forward Matt Mustchin.

The impressive Lopez-Fleming inflicted the initial damage with a long arcing run before being felled by a high challenge.

From the penalty line-out, Mustchin broke away from the melee and wheeled over the line, reaching full stretch to place the ball down. Hodge confidently banged over the conversion.

Then came a stirring reply from the Ospreys. First - also from a line-out close to the corner - the ball was flashed across the field for Jonny Vaughton to finish in style.

The score acted as a real spur to the visitors and it was no surprise when flanker Steve Tandy picked up a simple second try when he was left unmarked on the left.

Edinburgh's problems intensified six minutes after the restart when former Springboks star Stefan Terblanche stretched their lead with a penalty.

Terblanche returned to the spotlight almost instantly to effectively seal the fate of the Gunners.

It was another Murrayfield tale of woe for Phil Godman. Less than a week after his blunder paved the way for Italy's shock Test win, his insipid challenge allowed Sonny Parker to make a clean break before giving the scoring pass.

Jason Spice slotted the conversion to leave Edinburgh trailing by 13 points with time slipping away.

And even worse was to come when Marshall turned on the pace and power to make sure of the valuable bonus point.

Cairns clawed back a touchdown for the hosts - but the Ospreys had the last word when substitute hooker Huw Bennett ploughed over.