Andrew Scott, 41, was born and raised in Dublin. Recently seen in the BBC adaptation of King Lear, he is best known for playing Moriarty in Sherlock, and for starring in Robert Icke’s production of Hamlet, which transferred from the Almeida to the West End last year. In 2008, Simon Stephens wrote Sea Wall – a monologue about grief – for Scott; it is being revived as part of the Old Vic’s bicentenary celebrations.

How is it performing Sea Wall alone on stage?
This one I love. I did it at Edinburgh, and you could actually see the audience. There isn’t any separation, and the house lights are usually half-up.

The play gets to some big questions pretty quickly – such as, do you need God when terrible things happen?
The idea of goodness, morality and kindness, and that you can possess those qualities without an organised faith… I think a lot of people of my generation feel that. People want to be kind and good, and have a sense of community, all that the church used to bring.

You were brought up as a Catholic. Does it still hold anything for you?
No, it doesn’t. I hid away from it before, but now I feel like I actively reject my upbringing. Not in an angry way – I don’t feel angry any more. A lot of family and friends do still believe, and you’ve got to exist with that. But over the past five years I’ve been really interested in the idea of spirituality and mindfulness – just being here. I do find it troubling, being on a train and looking round and everyone is on their phones. We can be addicted to not being here, to always being somewhere else. Having all this information is so new; you realise, God, I actually can’t sit still. Just to be there and not to be looking for a little high all the time… That will define our age.

Does theatre give us a way to come together?
It is nourishing. And some of the things phones bring us do nourish us – you can read a book, it’s not all pouting on Instagram. [Theatre] gives you community. But I really don’t want to be someone who just says “Get off your phone”, because of course there’s community in Snapchat or whatever – [young people] are getting something from it that we used to get drinking beer down by some lake.

How was playing Hamlet?
It was extraordinary. I’m still absorbing it. After I finished, two weeks later I did King Lear: I had a Shakes-year, boom-boom. But it’s the stamina. Sometimes I thought I can’t do it – three hours and 50 minutes, twice on a Wednesday and Saturday. And it’s not light material; you have to go to a dark place.

What was your way into that part?
I really wanted it to be engaging for people who’d never seen it before. Rob Icke and I wanted it to be a play that would ignite our 14-year-old selves. And the big thing was to try to speak the language in as conversational a way as possible. To attack the play for what it is rather than what you think it is – because it’s so famous. I do think it is the greatest play ever written.

It might be the greatest play ever written – but do we do it too often?
There are a lot on! You have to have a really sound idea – you can’t just barge in. There has to be a real reason behind it. I felt very proud of our production: 28,000 young people came to it. Something like half of the audience in the West End had never been to the theatre before. And that’s an achievement.

A first bad experience of Shakespeare can kill it for you, whereas a good one can set you up for life…
I always think of it like rap music – there’s the rhythm of the thing, and even if you don’t get every word, it’s electrifying. I just hate the idea of Shakespeare being put in a glass box, like something that’s dead.

You played Hamlet hot on the heels of Sherlock co-star Benedict Cumberbatch. Was there rivalry?
There was no rivalry. It has to be your own thing, you have to bring who you are to it – so it shouldn’t be similar.

Hamlet may be the best part – but what’s the worst part you’ve ever had?
I played a Christmas bauble at the Royal Court. It was at this international festival, which are cool things – but I couldn’t do anything playing a Christmas bauble. I didn’t even get a costume, I just had to mime!

Did you like Shakespeare at school?
I loved Shakespeare as a kid. We used to have these drama competitions in Dublin, in deserted atmosphere-less school halls, with nervous mums and some priest slowly pulling a curtain open: “Competitor number three, an extract from Romeo and Juliet.” I got to play, when I was 14, Richard III, Shylock, King John…

How big an impact did Sherlock have on your career?
Well, I’d worked a lot before it, but it definitely opened doors for all of us. I’m grateful to have been in it.

You almost studied art. Is it still an interest?
Yes, it’s still a big passion of mine. I’ve been getting into linoprinting recently. It feels like magic to me.

Which artists’ work do you enjoy?
I live near Tate Modern and sometimes, when it’s late opening, I go in when I’ve had a hard day, and just walk around. As much for the particular quiet as the art. David Hockney is my all-time favourite artist.

Did you go home to Ireland for the abortion referendum recently?
Unfortunately I couldn’t, because I was working. And I was really scared. But oh my God, what a day. Another great day – because we had the marriage referendum a couple of years ago which was just so thrilling. It was a great day not just for women, but for humanity. Go on Ireland.

Sea Wall runs at the Old Vic, London SE1, 18–30 June