The Welsh side scored two tries, threw away two more and missed a couple of goal kicks for good measure. Their failure left Leicester well in the hunt and, as it turned out, within reach of a try bonus. They scored four tries after the interval to take the lead in pool three of the Heineken Cup, which will surely be the most tightly-contested group in the tournament.

It was a remarkable turnaround in fortunes, based largely on the home team’s forward power. Well though the Ospreys played at the set scrums, they suffered a crisis in the lineout and in loose play struggled against the Leicester forwards, among them one of their own, Darren Morris, whose ball-carrying damaged his former colleagues several times.

That undermined the supply of ball to their talented backs, where Gavin Henson — against predictions — started his first match since playing for the Lions against New Zealand on July 2. Yet Henson and his colleagues will have taken heart from their performance for the return encounter at the Liberty Stadium next Sunday.

“That’s the first match for about a year when I haven’t felt any pain in my groin,” Henson, who feared at one stage that he might not play rugby again, said. “I know we lost but I’m over the moon, to be honest.”

He had the opportunity to mark his return with a try after only four minutes but, remarkably, turned back into Ollie Smith’s tackle when all he needed to do was keep running to the line, a mistake that was repeated when James Bater cut a delightful angle but looked for contact as the Leicester line loomed, allowing Harry Ellis to insert his body between the ball and the turf.

“When you have been off the pitch for so long, everything seems to happen that much more quickly,” Henson said, but it was his deft pass that set Sonny Parker on his way to the first try after Andy Goode’s first penalty goal had given Leicester the lead. Goode’s kicking mingled the outstanding with the atrocious and several of his colleagues tried to match him as Leicester, as anxious as the Ospreys to look wide, found it impossible to finish a variety of promising moves.

Goode chipped over a second penalty but the Ospreys closed the half with an outstanding set-piece try: Ian Evans won a lineout in his own half and Richard Mustoe, picked ahead of Shane Williams, came off the wing to take Shaun Connor’s pass and carve open the defence before handing the try to Adrian Cashmore.

Connor missed the conversion, a penalty and a dropped goal around half-time and it took a wonderful 60-metre run by Geordan Murphy to spark Leicester into life but, once he had done so, they were irresistible. One glorious chance had gone begging, when Shane Jennings threw a forward pass to the unmarked Sam Vesty, so Leicester opted for a close-range lineout, Louis Deacon made the catch and his younger brother, Brett, drove over.

No more than 26 minutes remained but it was enough for Leicester to confirm their growing superiority. The Ospreys could not shackle Martin Corry and the England captain’s burst from a ruck paved the way for Ellis to take advantage of a gap and scoot around Cashmore to the posts.

A clutch of tactical replacements did nothing to help the Ospreys escape their 22, as they were pinned there by the length of Goode’s touch-finding, and the fly half’s diagonal chip created Leicester’s third try. The unlikely figure of Ben Kay loomed up on the right wing, with support from Murphy, and George Chuter took the ball to score and complete an excellent afternoon’s work.

Leicester secured their third bonus point in three games — the Ospreys, bottom of the pool, have yet to take one — with two minutes left. The formula is age-old at Welford Road: another penalty to the corner, Louis Deacon won the lineout and Austin Healey, now at scrum half, was in the midst of the pack for the try.

SCORERS: Leicester: Tries: B Deacon (54min), Ellis (60), Chuter (71), Healey (78). Conversions: Goode 2. Penalty goals: Goode 2 (21, 34). Ospreys: Tries: Parker (25), Cashmore (40+1). Conversion: Connor.

SCORING SEQUENCE (Leicester first): 3-0, 3-7, 6-7, 6-12 (half-time), 11-12, 18-12, 25-12, 30-12.

LEICESTER: S Vesty; L Lloyd (rep: A Healey, 51), O Smith, M Cornwell, G Murphy; A Goode (rep: R Broadfoot, 80+2), H Ellis (rep: D Hipkiss, 78); A Moreno, G Chuter (rep: J Buckland, 80+2), D Morris (rep: M Holford, 72), L Deacon, B Kay, B Deacon, S Jennings (rep: L Abraham, 80+2), M Corry.

OSPREYS: A Cashmore (rep: S Williams, 65); S Terblanche, S Parker, G Henson, R Mustoe; S Connor (rep: M Jones, 5-12, 76), J Spice; D Jones, B Williams (rep: H Bennett, 65), A Jones (rep: A Millward, 65), A Newman, I Evans, J Bater, S Tandy, J Thomas.

Referee: J Jutge (France).

Attendance: 16,815.