The Last Trump appears in the Bible in 1 Corinthians 15:52:
In a moment, in the twinkling of an eye, at the last trump: for the trumpet shall sound, and the dead shall be raised incorruptible, and we shall be changed.
In this context, the idea of the last trump is connected with the resurrection of the dead and the Day of Judgement.
However, there is also reference to the sounding of a seventh trumpet in Revelations 11:15, where it marks the ending of a period known as the Tribulation. This is also viewed by some as the last trump.
Can anybody clarify this rather confusing subject?
As used by Julia in Brideshead Revisited, the idea of the Last Trump appears to be linked to the idea of tragedy being imminent.