When Heather Al-Yousuf, first met her husband of 28 years, they both felt a strong connection to their own faiths.But their love was not straightforward as Heather is Anglican and her husband is Shia Muslim.
"It is almost like there is something they recognise about each other, there is an unconscious connection there - same kind of families, same kind of faith informing how they live life," Mrs Al-Yousuf says. However, inter-faith relationships also challenge both faiths. But Mrs Al-Yousuf, who now lives in Oxfordshire, thinks this figure could be higher as there could be many more unmarried couples who choose not to marry due to the complications caused by selecting a ceremony.When two planes hit the World Trade Centre on 9/11 in 2001, Heather Al-Yousuf says she felt sick when her husband suggested they recite the opening Sura from the Koran."I had this gut feeling, no I don't want to go there, I feel sick at the whole thing about Islam."But then I connected it to my husband and our families, not to those people who did that."That was quite an important psychological moment for me to get through, that negative association with all things Islamic." The family did recite the Sura, and Mrs Al-Yousuf also sang the Lord's My Shepherd.
"I suppose, when the chips are down, that's the religious experience that you want to hand on to your children, regardless of what else," says Mrs Al-Yousuf.
The Al-Yousuf's decided to bring up their children in both religions.
"We do both, if it's Eid, the children fast, but maybe not the whole of Ramadan." Inter-faith couples can gain support from the Inter-faith Marriage Network, they meet every few months in London and also have a strong online community.
The Christian Muslim Forum, an organisation that promotes a better understanding between Muslims and Christians, has also recently produced ethical guidelines to help faith leaders give pastoral support.
Heather Al-Yousuf has contributed to these and works to help many inter-faith couples.
"Very often, the couples I know, have been together for a very long time before they make that [marriage] actual choice.