George Plimpton was late. On the way from the airport his car had gotten caught in the traffic around the shah's demonstration's and it took him more than an hour to get out to Silver Spring.

At another time he might have been on his way to see the shah himself, might have been there in the White House instead of edging around it. He has always been in the middle of things by design - participatory journalism he calls it - and sometimes by coincidence. He boxed with Archie Moore, pitched to major league hitters. He wrestled the gun from Sirhan Sirhan in the dark Los Angeles hallway where Robert Kennedy was killed. The author of "Paper Lion." star of television specials, editor of "The Paris Review, one of the most B of the BP'sknows everyone, royalty not excluded.

But he wasn't late for the shah. He was late for the cocktail party celebrating the grand opening of new offices for Business Machines of America (local outlet for Olympia typewriters) in a former bank building in suburban Maryland.

They paid him $2,000 to come - not to deliver a speech, mind you, but just to come. To stand around with a drink in his hand, nibble delicacies from the caterers' giant fruit type-writer, and chat with whoever cared to chat. $2,000.

Warner Wolf, the former Washington sportscaster, was there, too. $1,000.

It was PR man Bill Rolle's idea to hire "celebrity hosts." "People in this town are invited to a lot of parties. Your bank presidents, the press, generally they'll only turn out for personalities" (Can't fault his logic here). So Rolle and BMA president Lou Statzer went over a list.

They tried Billy Carter. He's good at standing around drinking. But he costs $5,000, and that seemed too high. They thought of Margaux Hemingway, but she wanted expenses from Paris, plus five grand, and that, really, was out of the question. Sinatra - he would be a big draw for sure - was not interested. Same for Cary Grant.

So, Plimpton. "We had sort of an informal poll, you know," said Rolle. "You'd be surprised. Plimpton's name recognition far exceeded a lot of those more expensive ones."

And Wolf? "Well, you know how TV is. You're off the air and . . . But I think a lot of people remember him around here."

Plimpton appears at the door: 6 feet 4 inches of Ivy League. He's aging, you can see, but he's aging elegantly. His hair is silvering. The well-tanned skin under his eyes is sagging. But one of the world's most ingratiating smiles is still there.

He's ready to charm. And willing. And not sure what else here is to do here among the typewriters and calculators. "Just lead me anywhere you want me to be led," he tells his hosts.

There are a lot of ex-athletes around - men with open Quiana shirts and broad shoulders, Tom Roy a 6-foot-10-inch former Maryland All-American, as they say. Mo Howard, another Maryland ball player, is introduced to a reporter. "Mo," says a young PR woman, "is interested in writing." What kind of writing? "Well, I think sports, don't you?" "You should talk to George Plimpton." Howard looks blank, then looks at Plimpton. "He writes sports?"

A man in a blue double-knit suit has taken Plimpton aside. He wants to talk to him about books. He's really into motivational literature, he says; has Plimpton read "Think and Grow Rich?" Plimpton says he hasn't. The conversation slows down a bit. Plimpton edges away graciously.

The bags under the Paper Lion's eyes are beginning to sag more noticeably. He says he's beginning to feel guilty about this whole thing. He's used to traveling constantly to give speeches and lectures, to officiate at functions - the blowing up of the world's largest firecracker (the famous Fatman II), a Bennington commencement, a mock mutiny aboard a South Seas cruise ship - but this is the first time he's ever been paid simply to attend a cocktail party.

He says he wishes he could make a speech or something. "This way everyone asks the same questions over and over. I start to tell them about Alex Karras and someone comes up and takes my away to meet someone else." Doesn't that happen at the cocktail parties he goes to for free? "Thank God, no."

He is talking to the two or three people who stand around him for more than a handshake. Talking about the great writers of the day, and the great artistic risks they take. "I don't take risks like that," he says. He talks about their genius. Their difficulties. Capote. Mailer. Styron. All over 50 years old now.

"Poor Truman," says Plimpton. Styron? "One doesn't know, really." Mailer? "He's never been happier or looked better. He has this lovely young woman - who's carrying his child . . . out of wedlock. But he looks tremendous." He says it as if Mailer had just been named an All-American.

And Plimpton? "Turning 50 (a few years ago) just seemed to speed me up. I've got two books out right now . . ."

But what about this party? Why? "Purely mercenary. I have a family to support. Children." No one ever thought Plimpton, New England aristocrat that he is, is poor. But there are few people rich enough to turn down a $2,000 cocktail party.

"If I'm losing anything," he says, "it's that business of being in the right place at the right time. I've been playing hockey with the Bruins, and the other night I left the game for awhile to talk to a group of executives. When I got back I found out they'd had one of the biggest bbrawls ever on ice."

An MBA executive interrupts. "I'm going to sell you a typewriter." (The evening is wearing on.) Everything on the machine is automatic. $840. "I hear it takes your manuscript and eats it," says Plimpton. No smile from the salesman.No sale.

But the finale is coming. Many of the guests are into their fourth of fifth pina colada, and it's time to draw for the door prizes. Warner Wolf pulls the first card from the box. The winner has gone home. Much giggling. Plimpton pulls the second card, but it's discovered that a salesman has already sold the prize. Some people will sell anything.

Finally, it's over, and Plimpton falls into a conversation with Warner Wolf, who says he's going to Paris soon.

"Get outside the city," says Plimpton, who should know, "to the little towns." And then he asks politely whether Wolf, now 40 years old, has ever been to Paris.

"No."

There is just a bit of a pause. "Wow."

Out of the door. Goodbye to the host. Goodbye typewriters.

A heavyset man in a houndstooth jacket (looks like he might have been a fullback) is talking to a woman on the steps of the remodeled bank.

The fullback suddenly raises his voice, keying off something his lady friend has said. "He's not handsome. ARE YOU GEORGE? He looked funny in a uniform. DIDN'T YOU GEORGE?"

George smiles, turning but not breaking stride, "Yeah, and I'm proud of it." He waves.

Tonight, Friday, George Plimpton is giving a party in New York, at ringside in Madison Square Garden, to celebrate the publication of one of his new books, "Shadow Box." He has invited Mailer and Vidal, and he's toying with the idea of pairing off other of his guests in the ring: Jackie Onassis and Ron Gallella; John Simon and Liza Minnelli. Some time in the future he's thinking of playing with the rock group Kiss. (Imagine George Plimpton in vampire make-up on toothsome platform shoes.) He's going back to his element.

He's also beginning work on his first novel. As a writer he is beginning to take risks he never took before. The book will be about an aging photographer who is always in the right place at the right time, and takes the wrong picture.