IT features 450 faces, was 23 years in the making and has been seen by the general public just a handful of times.

Now a historic painting featuring some of the greatest Victorian Scots is the centrepiece of a major new London exhibition.

The first painting to be drawn from photographs, the Disruption Portrait by David Octavius Hill captures the birth of the Free Church of Scotland and has spent most of its life hanging in the Free Kirk’s Edinburgh headquarters.

The church formed in 1843 when the majority of the evangelical ministers of the Church of Scotland resigned over state interference in its affairs.

Under the patronage system of the day, landowners could nominate and present ministers of their choice to congregations, regardless of whether worshippers wanted them.

The new denomination was formed to ensure independence from the state, with Hill present for what was known as “the Disruption”.

To create the 11-feet wide work, he teamed up with St Andrews-born photography pioneer Robert Adamson to take calotype shots of those present.

However, Adamson did not live to see the result, dying in 1848, 18 years before the last brush strokes were made.

The result captures not only a key moment in history, but also a cross-section of society which includes many of the era’s most notable names.

Open from tomorrow until the end of September, the Tate Britain’s Painting With Light show will see the painting hung alongside some of Adamson’s original photographs.