The most important commission for a Scottish Catholic cathedral since the 16th century Reformation is to be announced on Friday by Glasgow's Archbishop Mario Conti for the city's St Andrew's Cathedral.

Peter Howson, Scotland's most famous painter, has been chosen to complete a huge, iconic work, to be placed in St Andrew's Cathedral when it re-opens after renovation works in 2010.

The painting, expected to be the largest crowd scene ever painted in Scotland - with upwards of 600 individual figures included - will become the focal point in the renewed worship space.

Renowned Scottish composer James Macmillan will be present at a press launch this week to speak on the historical and social significance of the commission and the influence of religion and art on society.

Peter Howson will unveil initial studies at the launch and the cathedral space where the painting will be placed will be open for viewing.