Some 550 people attended a Christian Institute meeting in support of Ashers Bakery at the Seagoe Hotel on Monday evening

The McArthur family, which owns Ashers Baking Company in Belfast, is challenging a ruling that their refusal to make a cake with the slogan ‘Support Gay Marriage’ was discriminatory, with an appeal to the Supreme Court to taking place in Northern Ireland on May 1 and 2.

The Christian Institute, which is providing legal support to the family, has organised a series of support meetings this week, though the McArthurs will not be attending in person.

With 20 minutes to go before the start of the meeting at the Seagoe Hotel on Monday, it was clear that the 360 seats were not going to be enough.

Staff hurried to bring in extra seating to cope with the eventual crowd of 550 people.

Outside, drivers abandoned cars in the packed car park while others parked outside down the road.

The meeting opened in prayer and the mood was dignified.

After speaking to many of those present, it was evident to Christian Institute Northern Ireland officer Callum Webster why the turn-out had been so large.

“People are concerned about the MacArthur family, but they are also very anxious about what is happening and see the wider issues at stake,” he said. “They see how they could impact on them and their businesses and how they live out their Christian faith in their day to day lives.”

Those attending were given a presentation on the organisation, which was started by teacher Colin Hart and now employs 43 staff, campaigning on issues such as sexuality, abortion, euthanasia and abortion.

Then deputy director Simon Calvert told the audience: “I know that the McArthur family will be so encouraged that so many of you turned out tonight to show your support for them”.

He voiced concern that anti-discrimination legislation which had been drafted to protect people of faith now risked “being turned into a sword when it was meant to be a shield of protection”.

And he noted that the McArthurs had drawn the support of gay rights campaigners Peter Tatchell and Jeffrey Dudgeon.

In the course of hearings to date, he said, one judgment against the McArthurs had also rebuked the Equality Commission for failing to offer the family legal guidance.

The precedent being set, he said, could in the future see atheists, Muslims, Roman Catholics and the gay community itself all caught in similar discrimination cases where they feel unable to provide business services which might compromise their convictions.

Simon Calvert told the audience that former BBC legal correspondent Joshua Rozenberg suggested judges have ruled against Ashers to date because Northern Ireland has not accepted gay marriage.

Mr Rozenberg said previously: “...there is no prospect of gay marriage in Northern Ireland, the politics of the Province being as they are.

“And if you want my personal opinion that has very much informed the way that these judges have come down in this way.”

He added: “It is not a very legally sound argument... but I do see why they wanted to do this.”

A short video of the Portadown event on the News Letter Facebook site prompted vigorous debate. One contributor said: “It’s a business, businesses don’t have beliefs. Not everyone is Christian get over it ...They can’t force their beliefs on others.”