Traditional Retreat at Douai Abbey 4th -6th July 2008

From the Catholic Herald:-

Archbishop Leo Cushley has reminded his flock that “attending Mass on Sunday is a solemn and binding obligation”, and that missing Mass is a grave sin....In 1679, Pope Innocent XI officially condemned the idea that missing Mass on Sundays and Holy Days of Obligation is not a mortal sin.

However, as Archbishop Cushley noted, this does not apply if illness or some other grave cause makes getting to Mass impossible.