McGregor, a household name whose career has taken him from derelict Leith backstreets as junkie Mark Renton to a galaxy far, far away as light-saber wielding Obi-Wan Kenobi, is long established as one of Britain’s best acting exports.

But he admits there’s one film that stands out ahead his other, more notable screen achievements – albeit for the wrong reasons.

Appearing on the latest edition of Nick Grimshaw and Angela Hartnett’s Dish podcast alongside his Long Way Round co-star Charlie Boorman, McGregor, 54, claims the film is so awful he’s never seen it – and won’t even name it.

Discussing his love of the bagpipes, the Scottish actor admitted he started playing the instrument while shooting the hated film on location in London, months after completing work on 2012 release Salmon Fishing In The Yemen.

He said: ‘I come from a long line of drummers, you know, I was a side drummer in the pipe bands, I was in the school pipe band, I was in the regional pipe band, but always on the side drum.

Ewan McGregor appears on the latest edition of Nick Grimshaw and Angela Hartnett’s Dish alongside his This Way Round co-star Charlie Boorman

Discussing his love of the bagpipes, the Scottish actor admitted he started playing the instrument while shooting his most hated film on location in London

‘My dad had been a drummer before me, my uncle, there’s a lot of pipe band in my family… so I got a set of bagpipes and I found a teacher.

‘By the time I got my pipes, I was now making another film in London, which I won’t name ’cause I hated it, and I never, never even watched it, it’s a rubbish film, but anyway.

He added: ‘You can figure it out. It wasn’t Salmon Fishing… I loved Salmon Fishing, that was a lovely film. That was where I got the idea.’

Shortly after Salmon Fishing In The Yemen, McGregor featured in English language Spanish disaster film The Impossible – shot primarily on location in Spain and Thailand.

The following year he played Elmont in the star-studded CGI fantasy Jack the Giant Slayer, with various locations across the English countryside used as rural backdrops.

But in 2013 he was back in London for the first time since the release of Salmon Fishing In Yemen after accepting a role in Johnny Depp’s much maligned crime drama Mortdecai.

The David Koepp directed film, adapted from author Kyril Bonfiglioli’s Mortdecai book series, featured Depp in the title role and McGregor as Inspector Alistair Martland.

A star-studded cast-list also included Gwyneth Paltrow, Jeff Goldblum, Olivia Munn and Paul Bettany.

While he refused to name the film in question, it may well have been 2015 flop Mortdecai (pictured)

‘I never, never even watched it, it’s a rubbish film, but anyway,’ he said while discussing his career with Grimshaw and Hartnett

But Mortdecai’s big billing and cinematic London backdrops couldn’t prevent it bombing at the box office, with US theaters withdrawing the film just three weeks after its release.

Reviews of the films were equally unfavourable, with The Huffington Post claiming ‘it seems destined to be rated as the worst film of 2015, and deservedly so.’

Elsewhere, The Guardian’s Mark Kermode dismissed it as ‘a dismally unfunny comic thriller with only one decent joke.’

Dish from Waitrose is available on all podcast providers. 

The David Koepp directed film, adapted from author Kyril Bonfiglioli’s Mortdecai book series, featured Depp in the title role and McGregor as Inspector Alistair Martland (pictured)