We have all been there: just sat down for dinner, the baby is crying, even "X Factor" is on, and two young (usually American) well dressed guys knock on the door, wanting to talk about what they see as the true, restored gospel of Christ.
Many Christians who otherwise love the opportunity to talk about Jesus with interested people would jump at the chance to talk to a non-Christian. But when it's someone at the door who has a confident answer, often using the Bible and having a very different system of belief to us, it doesn't seem like the great witnessing opportunity that it could be.
More than ever the Mormon Church - or its full title, the Church of Jesus Christ of Latter-day Saints - is getting exposure in the news. Republican US presidential candidate Mitt Romney is a very committed Mormon, with a long family background in the movement.
But who are the Mormons? Is their church a cult? Is it another Christian Church? Are Mormons people Christians should consider as part of our mission field?
The Mormon Church which today has a 14 million strong membership and has around 55,000 full time missionaries worldwide, exists on the foundation of a young Joseph Smith, living in Palmyra, New York.
Smith had a vision of God the Father, with Jesus telling him that all of the churches in the world were wrong and their creeds were abominable, and that he would establish the restored true Church to the world.
Since then Mormonism has certainly mellowed in the view that all Churches are so wrong. But they still very much see their church as being the place where you will find the fullness of God's truth, and the Church you must be a part of if you are to receive your "exaltation", which is to become a god over your own kingdom.
A famous phrase that came from the 5th Mormon President Lorenzo Snow is "As man is God once was, as God is man may become".
Within Mormonism God was once a man as we are now, Joseph Smith said, but we also cannot receive this exaltation by faith alone. The book of Mormon in 2 Nephi 25:23 says we are saved by grace after all we can do.
This is a massive contrast to the biblical teaching in Ephesians 2:8 that we are saved by grace through faith and not of ourselves: it is a gift of God.
Twelfth Mormon president Spencer W Kimball, whom Mormons would believe was a prophet like Moses and Isaiah, wrote when he was a Mormon Apostle that; 'One of the most fallacious doctrines originated by Satan and propounded by man is that man is saved alone by the grace of God.'
So we have in Mormonism a totally different God and gospel to the biblical one. We see in John 17:3 that eternal life is to know God and we also see in Galatians 1:8 a harsh warning about the teaching of other gospels.
For most of my time as a Christian I have clearly known God's call on my life to reach these people.
When at college as a new Christian I did an assignment describing and evaluating Christian cults. In response to hearing the claims of the Mormon and Jehovah’s Witness Churches I looked for myself at what the Bible teaches about Christ and salvation.
What I saw is that they were very different to the claims of these groups. For me it seemed natural that I should seek to reach them with the Biblical gospel of grace given by a Saviour with the fullness of Deity dwelling in Him.
In the last two years I have turned the tables and gone to Utah on mission trips, engaging Mormons in respectful discussion while they walked to their seats in their thousands to watch a re-enactment of their history and theology at the Manti Miracle Pageant. Christians in Utah and surrounding states see this as their best opportunity each year to witness to members of this group.
Dave Mitchell from Florida who regularly goes, said, 'I travel 2,254 miles to Manti each summer (at my own expense, on a retiree's fixed income) only because my heart is broken for the Mormon people. They think they know the true God and the true Gospel, but they are headed for eternal destruction and they don't even realise it.'
For the first time ever the Mormon Church is hosting a similar event outside of the US. This event is going to be in Chorley on the grounds of their temple.
It's anticipated that every night of this event which is being held in the last week of July and the first week of August 2013 will have hundreds of Mormons coming each night. This is the greatest chance in many a year for Christians in the UK to witness to these great people.
For some of you this will sound like a great opportunity. If that's you please email me on email@example.com
For many others who would not even be sure what to say when you get a knock on the door from members of these groups, please be assured you are not alone.
My ministry UK Partnerships for Christ
exists to equip the UK Church in how to confidently and lovingly witness to Mormons and Jehovah's Witnesses when they come into contact with them, by delivering seminars at your local Church and providing articles to help people understand these groups. Equally I would love to hear from you if this would be of interest.
Every day members of these groups knock on many doors countrywide. My honest hope and prayer is that more and more Christians will act on 1 Peter 3:15 and give an answer for the hope that they have.
Bobby Gilpin is the founder of UK Partnerships for Christ