• A projector and two OHTs, available here: an equilateral triangle and the other an outline of a shamrock.
• A focus table covered in a green cloth, with three candles.

• Introduce the theme - you could say something like this...

  'In today's act of worship we are going to be thinking in a new way. It's called 'three-in-one thinking'. Christians do this when they think about God in three ways: God the Father, God the Son and God the Holy Spirit, but still one God. For shorthand, they describe this three-in-one way of knowing God as the Holy Trinity, and it's a bit of a puzzle! So the Christian calendar has set aside one day each year, called Trinity Sunday, when people can have time to puzzle about this mystery.
  
  Let's see if we can do some three-in-one thinking to help us think about this puzzle.'

• Project the image of an equilateral triangle. Explore the features of the triangle. Encourage pupils to describe its features. Turn the image round and view it from different sides.
  
  
• Summarise the discussion...

  'Whichever way you look at it, there are three sides that make up one triangle - I wonder if this idea might help us with some three-in-one thinking?'

• Project the image of the shamrock and explore its features. Then tell the story of St Patrick...
  
  'The shamrock is a plant that grows in Ireland - it's a kind of clover. St Patrick was a Christian missionary in Ireland many, many years ago and he later became Ireland's patron saint. He and his friends used to puzzle about the mystery of the three-in-one God. The story goes that one day his friends asked Patrick to explain the mystery of the Trinity. He looked at the ground and saw shamrocks growing amongst the grass at his feet. He picked one and showed it to his friends and said, "Look at this beautiful little shamrock. Do you think it has one leaf or three?"
  
  Patrick's friends looked and looked but they couldn't answer; the shamrock looked like one leaf but it clearly had three parts. Patrick reassured them, "The mystery of this shamrock is like the mystery of the Trinity; there are three parts but they are all part of one."
  
  Christians around the world continue to puzzle about the mystery of the Holy Trinity: God the Father, God the Son and God the Holy Spirit - one God but three different ways of knowing about God. They use symbols based on the triangle pattern or plants like the shamrock to help them with this kind of 'three-in-one thinking'.
  
  
• Turn off the overhead projector and shift your attention to the green focus table.

'Praise God from whom all blessings flow,
Praise him, all creatures here below,
Praise him above, ye heavenly host,
Praise Father, Son and Holy Ghost.'