Although we can't see it from where we are standing, the National Theatre's huge electronic display has Patrick Marber's name up in lights. "A new play by Patrick Marber" it says, which could be referring either to The Red Lion, his first play in to be staged in eight years and set in the grubby changing room of a down-at-heel football club, or Three Days in the Country taken from the 1855 Turgenev classic about summer love (A Month in the Country), which opened this week. Starring John Simm and Mark Gatiss within a cast of 18, it's the biggest production Marber has directed.

"I'm not a smoker," he says as he lights up. "I just have the odd one since I started working here." By 'here' he means the National of course. There can be very few writers who have had two works performed at the same time.

"I'm having an incredible year," he admits in a believe-that-and-you'll-believe-anything kind of way that is the closest Marber gets to sounding positive. But it's true, this a good year. Not that there haven't been good years before. His stellar rise in comedy with The Day Today and as the co-creator of Alan Partridge were followed by plays - Dealer's Choice and Closer - which, for many, marked him out as the most talented dramatist of his generation. But compared to the last seven years or so, which were defined largely by his writers' block, things are looking up.

We are standing on a National Theatre terrace overlooking the Thames. The sky is the colour of the river's swill and through the drizzle to our right St Paul's still somehow lords it over the much taller buildings surrounding it. Somewhere between Wren's dome and the Barbican's towers is Marber's home where he has been living since moving back to London after his "finding his inner farmer" period in rural Sussex, where he raised pigs and sheep.

"When I was a kid,'' he says, ''I thought the National was spectacular and modern and exciting and strange. The height of my ambition was always to work here. That was the thing I most wanted, as any kind of writer, actor or anything." So here he is, back at the height of ambition. Although the Oscar nomination received for Notes On A Scandal, the screenplay that he adapted from Zoe Heller's novel, must have felt pretty high, too.

Reading through interviews conducted with Marber over the past decade reveals a pattern. Most dwell on his famed writers' block, which hit hardest after 2012. And it wouldn't be a Patrick Marber interview if it didn't mention the poker habit that cost him thousands, including the time when, in his 20s, his father, a City analyst, came to the rescue to the tune of, it is said, £10,000. Marber no longer feels the gambling impulse - "I only play a bit of poker now. It doesn't excite me any more. It's totally gone from my system" - and anyway, with the three young children he has with his wife Debra Gillett (who is in the cast of Three Days in the Country), the stakes that come with a gambling habit can get uncomfortably high, even for a top tier screenplay writer such as Marber.

One of his more recent jobs was reworking the screenplay for Fifty Shades of Grey. The producers loved it. The novel's author E L James didn't. Marber holds no grudges. On the contrary. "I did 10 days' work on it, got paid, got fired. It was fine. I absolutely respect her position as a fellow writer. I like it that she went in and got complete control of the project."

Clearly, there have been more painful experiences in the fickle world of film. One of his unmade screenplays is an adaptation of Ian McEwan's novel, Saturday. That one didn't happen because "the company that paid for it, Miramax, went under." That was "bad news". The unmade screenplays remain "perfect" in Marber's mind, where he can watch the movie "in its perfect execution. I suppose like a composer whose music doesn't get heard. It's still there."

But back to those interviews and that pattern: they each have a sense of Marber emerging out of crisis. Even this one, we have already established, is defined by his "incredible year" and the suggestion that there were some incredibly bad years that preceded it.

"That's interesting," he says. "That makes sense for the shape of how I live. Crisis, calm. Crisis, calm. And, yes, plays tend to emerge out of crisis. They don't seem to be written in calm. Unfortunately. I need to address that. It doesn't surprise me that that's a pattern.Though I wasn't fully aware of it until you said it."

The most recent crisis has been the mid-life kind. It was anticipated by his 2001 play Howard Katz about a Jewish showbiz agent who has a series of angry (one way) conversations with God about the way things have turned out. Not that Marber, who is 50, was in mid-life crisis when he wrote it. But as he says, he writes "things that both foretell and describe a feeling. Then the feeling of middle age arrived. That was difficult. Still is. I don't like it. Didn't much like being young but I certainly don't like being old. I said that to my wife the other day. Imagine living with that."

So did – does – his crisis have a Jewish flavour in the way Howard Katz's does?

"My whole life has a Jewish flavour. I'm a Jew. I think of myself as a Jew first and Englishman second." This comes as somewhat of a surprise - not that he feels it but that this in some ways very English kind of Jew, expresses his identity so emphatically. "Really?" I say.

"Oh yeah. And I say that as a man who hasn't been to shul for 10 years. But I'm a Jew. Proud. That's what I am. It's deep in me. I'm also patriotic and love my country. But it's my race. It's my being. It's what I am." And then he stops as if something has told him "that's enough."

"Anyway, I didn't wander the streets like Howard Katz but I knew how he felt. And I now know better how he felt having lived it. I know his lostness."

At least for the moment, however, Marber is found. This, after all, is his "year of challenges". Not least of these is waiting for him in the NT's rehearsal rooms. "I thought I'd bloody do it because how often to you get a chance to direct your own play? And because I've been out of the game so much I thought 'I'm going to do it. I'm going to do everything." For Marber, a master of melancholy, this is heady, inspiring stuff. "Say yes!" is apparently the new mantra. "So here I am," he adds. "And I'm glad."

'Three Days in the Country' is at the Lyttelton until Oct 21.