He probably would have done all right if he'd stuck to the salad plates. But nowadays Jacobs counts more than dollars 50 bills. He doesn't know quite how much money he and his late partner Warren Casey earned from Grease ('People always ask and then say, 'Oh man, are those guys lying]' '), but what with the success of the original musical (1971), the Broadway opening (1972), the West End transfers (1973 and 1979), the movie spin-offs (1978 and 1982), the sales from the album (ad infinitum), the endless regional and amateur productions (ditto), we're talking never-need-work-again money, unless-we-want-to.
Jacobs wants to, but then he hasn't much choice. He lives in LA now - 'just because it's the hub, it's the business, it's movies, television, theatre, music and lots of actor friends' and he still writes bits and pieces (he created the pilot for Happy Days which went on to 'rip off' his musical). But most importantly, there's always a Grease on somewhere for him to oversee. He was out of town (touring as an actor in the Pulitzer-prize winning play No Place to Be Somebody) during the first ever production, an amateur show in a former trolley barn in Chicago which was such a hit there were touts. But since then, his stocky, ginger-whiskered form has become a familiar figure on set.
In the first Broadway production, which followed huge media interest, he mucked about with John Travolta, who was playing Doody. 'He was only 17 then, just a dumb kid. He was like 'Hey Jim, how d'you like my new boots?' or 'I'm just gonna go get some hamburgers, d'you want one?' ' At one point in the run, there was an understudy crisis and they asked Jacobs to step in for one of the actors. 'But I said no. I had hair at that time down over my shoulder and the moustache. This was 1972 remember. I wasn't going to go through all that . . .'
Later he sat in on auditions for the movie ('You may say Olivia Newton- John was too old, but look at Stockard Channing who played Rizzo. Stockard's like my age, God, talk about long in the tooth'). And in London in 1973 he goofed around with Richard Gere, who had his first big break as Danny: 'We were out doing all kinds of mischief. What mischief? Don't let me get into that. Let your imagination run to the wildest extremes of Soho excess in 1973 and you pretty much have an idea of the kind of places we visited, frequented, drank at, wasted our money at, generally got red-eyed and loony in.'
He's in London again this week for the opening of Grease at the Dominion Theatre. He keeps turning up to rehearsals to find they've been cancelled because of technical hitches. But he's making kooky expressions, twisting his mouth and putting on voices and mucking about for the camera ('Hey, showbusiness is my life,' he croons into a stray microphone). Three grazing cows are emblazoned across his denim shirt and he seems equally determined to enjoy himself. 'If Warren were here,' he says, 'he'd probably make a stand about things and maybe rightly. But I just don't want to get into a big fight. As long as they send me the cheque, who cares? I mean I'm not going to start phoning agents and lawyers. Hell, it's been running for 22 years.'
If the years have relaxed Jacobs, the show has loosened even further. In a way, it's not even his show any more. He based the original Grease - written with Casey, who was eight years older - on his schooldays in the Fifties. 'It was about having rock 'n' roll bands and leather jackets and beehive hairdos; about doing a lot of smoking and spitting on the sidewalk and giving the finger to people, about a guy getting a car in your neighborhood which was like suddenly, 'Oh hey, wow, you know so and so got wheels? Let's all go and hang out with him' . . .' As Fifties nostalgia has deepened, Jacobs's story has got lighter and lighter. Post-movie, he says, 'it's all let's throw confetti and balloons in the air, kids, and scream for the clowns and cheer for the acrobats'. Not that he seems to mind.
'The funny thing about it is that anyone who saw a previous version of it, always think they've seen something better than you've seen. When it went to New York, people said, 'Oh we saw Grease on Broadway', and people from Chicago said, 'You should have seen it in Chicago. Then it was really good.' Then the movie came out and people were saying 'Oh did you see the movie of Grease?' And others would say, 'Didn't you see it on Broadway? Oh well, you missed it because that was it; the movie's nothing.' So I don't know what they're going to say when they see this. Are they going to say, 'Didn't you see the movie? Because by now I think everybody has seen the movie. And anyway, it practically is the movie.'
One thing has worried him. Barry Gibb's 'Grease is the Word', one of the three songs written for the movie, is to be added to the stage show for the first time. 'But it was written to run over the credits and you don't get credits in the theatre. Realistically it doesn't sound anything like a Fifties tune, it's more a disco sound. So where to put it? After weeks of rehearsal and putting it hither and thither we've rigged up a sort of overture. I hope it works.'
And if it doesn't? 'There's something indestructible about this show,' he says. 'I've seen some really bad, bad productions, I mean I've seen some real clinkers. Like neighbours of mine in California, they'll say, 'Oh, Ruwanda Beach High School's doing Grease and our daughter's in it, will you come?' And I mean God, are they bad . . . But at the end, it gets a standing ovation. People scream and cheer, it just hits some kind of nerve or responsive chord. It's not like turning on MTV and getting Axl Rose or someone biting off chicken heads. It is just simple rock melodies and fun times. It's like it's got some kind of safety valve in it.'
Last year, Jacobs organised a reunion to celebrate the 20th anniversary of the Broadway show. He hired out the Sheridan Universal Hotel for three days and invited 600 guests - all of whom had been in Grease, sometime, somewhere. At one point, they had 30 Rogers standing in a row. Richard Gere sent a telegram, but Olivia Newton-John turned up. And so, too, did the actress who played Sandy in the first amateur production in Chicago. 'When I introduced her to Olivia,' says Jacobs, 'I said 'This is the real Sandy, the original Sandy' and Olivia was real gracious and sweet and said 'Oh we must have a picture together,' and Leslie just melted and was like 'Oh my gawd'.'
Travolta was there too, but no one could track down the original Danny from Chicago. 'He sort of disappeared,' says Jacobs. 'Though some one said he'd surfaced in LA and become a roofer.'
Grease opens at the Dominion on 15 July (Booking: 071-580 9562).