PLAYING 'GRACE' WAS A HIGH OLD TIME

London's Portobello Road is a bustling buyers' market for all kinds of products, from cashmere to controlled substances.

It's also the setting for one of several amusing scenes in Saving Grace, a breezy British comedy opening at selected theaters today.

In the movie, fiftyish Grace Trevethan, played by Oscar nominee Brenda Blethyn (Secrets and Lies), is showing off samples of marijuana grown in her greenhouse as a last-ditch effort to pay her debts.

The scene, filmed with hidden cameras among unwitting shoppers, almost put Blethyn in jail.

Director Nigel Cole did what he could to prevent that. Before the cameras rolled, Blethyn was introduced to 40 extras who would pose as potential customers while Blethyn improvised her lines.

"Could you remember 40 strangers when they mix in with 500 other real shoppers dressed just like them?" Blethyn asked. "Well, I couldn't.

"I was going up to complete strangers, saying, "Would you like to have a look at my stash?' or "Take me to your dealer.' "

A few non-actors took Blethyn's proposal seriously.

"Well, I scored twice," Blethyn said, with a prim accent that makes all this drug jargon sound elegant. "And a third person tried to make a citizen's arrest on me."

When Blethyn realized she wasn't dealing with an extra, she made a hasty exit while the offended shopper followed.

"He chased me down the road," she said. "Nigel came running, shouting: "No, please, it's Brenda Blethyn, she's our actress, we're making a movie!'

"It was terribly funny when this chap realized what he did. But good for him, in a way, going out there, trying to persuade people not to take marijuana. Good for him. He deserves a award or something."

The 54-year-old actor isn't a marijuana dealer; she just plays a reluctant one in the movie. Saving Grace is a farce along the lines of The Full Monty and Waking Ned Devine, in which decent (if eccentric) people stoop to improper or illegal measures when economic times are tough.

"In these films, nobody really gets hurt," Blethyn said. "The humor is born of joy. It's just extraordinary things happening to very ordinary people who would never do what they're doing in a million years.

"You can imagine your auntie, who I'm sure is terribly law-abiding. Suddenly, you read in the papers that she's been arrested for growing dope. In an odd way, that would be funny, wouldn't it?

"Grace is the most law-abiding citizen there is, but you have to understand her problem. Only then will anyone take that journey with her to solve it, by whatever means."

Saving Grace isn't merely a pot party, although High Times magazine readers have plenty of absurdities to smile about, including a grow- light system illuminating the sky like a close encounter with a UFO. Several scenes lovingly show cultivated plants with colorful buds the size of corn dogs.

Co-writer and co-star Craig Ferguson (The Drew Carey Show) said, yes, those are the real thing. With a difference.

"The pot in the movie is legal hemp, stuff grown on license from the British government," he said. "They are real marijuana plants, but grown in a special way to be really crap.

"If you smoke it, you wouldn't get high. It would be good for a pair of pants for Woody Harrelson, but that's about it."

For the record, Ferguson and Blethyn declared themselves non-users of the herbal drug, though Ferguson did confess to smoking a few "doobies" during his youth.

"No, I don't smoke at all, even tobacco," Blethyn said. "I have to say that I have eaten marijuana in a cake. Somebody said it was called a brownie. There's a Girl Guide unit in England called Brownies, so it sound rather funny to call them that. It didn't do much for me."

Both performers did express support for the legalization of marijuana. They noted therapeutic benefits for some ill people and regretted that U.S. and British law considers marijuana alongside harder drugs such as heroin.

"It's wrong to turn people into criminals," Blethyn said. "By legalizing it, I believe you could be putting a greater distance between the user of marijuana and the pusher who might promote some harder drugs as well. It should be totally separated from hard, malicious, vile drugs that ruin people's lives.

"I mean, tobacco and alcohol are legal. One kills and the other makes you aggressive. Actually, I think peanuts harm more people than marijuana. Some people are deathly allergic to peanuts, you know."