IN the summer of 1989, Maurice Johnston achieved the near-impossible: he united the Old Firm.

By completing what remains one of the most astonishing transfers in Scottish football history - when he signed for Rangers six weeks after appearing to have rejoined Celtic - Johnston managed to rouse equally the ire of both sets of supporters, disgusted with what had transpired for two very different reasons.

The Celtic fans fumed at what they felt was an act of treachery. Johnston was "their" player, a lifelong Celtic fan who had played diligently and effectively for the club for three seasons, and who had nailed his colours to the mast when, after being sent off in the 1986 League Cup final defeat to Rangers, he had blessed himself as he trooped off the field.

After two years with Nantes in France, Johnston was coming home to Celtic. Or so they thought. The transfer, though, would fall through due to tax issues and other complications, presenting Graeme Souness and Rangers with the chance to nip in and make him their player instead. They did not hesitate.

The Rangers supporters - not all but certainly a vocal minority - were not happy either. They were not keen on the idea of a well-known Celtic supporter and former player turning out for their club, nor with the fact that he was the club's first high-profile Roman Catholic signing, although not a particularly devout practitioner of the faith.

A joke did the rounds that the wife of a fervent Bluenose had given birth to quadruplets and called them Eeny, Meeny, Miney and Billy. Rarely mentioned is the fact that Johnston was actually from a mixed family, his father a lifelong Rangers fan.

Many other Rangers supporters welcomed the transfer. Some recognised they had signed a very good player and in the process weakened their rivals. Others simply bathed in a sense of schadenfreude, enjoying the way the Celtic fans were working themselves into such a lather as, in their eyes, the Prodigal Son became Judas Iscariot.

The more hardcore element of the Rangers support, however, would need to be convinced. Johnston would have to win them over on the field.

"I was sitting at Firhill one day and there was a fella close to us who kept saying, "he's not trying, we're playing with 10 men," and all that stuff, referring to Mo," recalled Andy Cameron, the Glasgow comedian and lifelong Rangers fan.

"Then Mo scored a goal and the big guy jumped up to celebrate. I told him I thought Mo didn't count and he tried to tell me it was Nigel Spackman who had scored. It took him a while to convince a few folk."

The season did not start well for either player or team. Rangers lost their first two games against St Mirren and Hibernian without scoring a goal. Then came Johnston's return to Celtic Park, the first Old Firm clash taking place on the third game of the season. Johnston, predictably jeered throughout, did not play particularly well, missing two good chances as the match finished in a 1-1 draw. Convincing the doubters and the dissenters was proving harder than he thought.

"Mo was hated by some of the supporters on both sides," added Cameron. "And when he didn't score at Celtic Park in the first game there were a few grumbles that he wasn't trying. It was a load of rubbish. He was a really good pro and Rangers ended up getting two good years out of him."

The goals, however, would soon start flowing. Johnston scored the winner at home to Aberdeen, and then repeated the trick against Hearts a few weeks later. With fellow striker Ally McCoist also in good form - after Terry Butcher's equaliser at Parkhead the pair shared the next 14 Rangers goals - Johnston was quickly adapting to life in a Rangers jersey and playing well.

Then, on November 4, 1989, came the second Old Firm game of the season, this time at Ibrox. On a damn, sodden Glasgow afternoon, Johnston would this time make a telling contribution against his former club.

The size of the Celtic support was reduced - their 7500-allocation was housed entirely in the Broomloan stand rather than in part of the main stand or enclosure as had been the case previously - but they made enough noise to make it uncomfortable for Johnston. Sometimes the abuse went beyond the mere vocal.

At one point as Johnston, perhaps unwisely, went to fetch the ball from near the Celtic support he was struck in the face with a half-eaten pie, the assailant huckled by the police and ushered out of Ibrox. Johnston quickly retreated from the scene, his arms shielding his face as further objects were hurled in his direction.

He would gain ample revenge later in the game. With the clock ticking down and a second Old Firm draw of the season looking likely, Rangers launched one more attack. Full-back Gary Stevens hared down the right before sending a cross into the Celtic penalty box. It lacked precision, however, and ought to have been cleared by Chris Morris. The Englishman, however, didn't make proper contact, the ball rolling into Johnston's path on the edge of the area.

Mo came instinctively to life. With one touch he got the ball out from between his feet and with the second he smashed in a low shot that beat the diving Pat Bonner at his right-hand post. With 88 minutes having been played, there was little doubt on either side that this would prove a telling intervention.

"The thing that always sticks in my mind is that he played the last 20 minutes of that game with his socks at his ankles," added Cameron. "Playing in an Old Firm game with no shinguards? That showed how tough he was. That goal was an incredible moment for Mo, a real turning point. If anybody was going to score that day it was going to be him."

Some players, for whatever reason, mark a goal against a former club with a muted celebration. That idea clearly never crossed Johnston's mind. Similarly, if there had been any Rangers supporters determined not to acknowledge anything achieved by this one-time Celtic forward than there was little evidence of it. Scan the footage of Johnston haring towards the Copland stand and all he encounters is a sea of utter delirium. Evidence of anyone sitting, arms-crossed in a staunch, Presbyterian show of defiance, is notable only by its absence. Johnston had finally won them all over and in the best way possible. The goal not only punctured Celtic's resistance but also had the effect of lifting Rangers to the top of the Scottish Premier League, above Aberdeen on goal difference. They would still be there come the end of the season, winning their second of what would go on to become nine successive championships.

Johnston was booked for his celebration for leaving the field of play but did not seem unduly perturbed by it. "Given the stick that I've taken it was good to score against them," he said. "It was especially [pleasing] to do it in front of the Rangers fans. After that I think they accepted me."