Mohamed Said was roughly halfway through a potted lecture on the pillars of Islam, taking in everything from the DNA of wine grapes to Malcolm X, when he brought up the troubled history of the building in which he stood.

“You can check every place,” he told the 20 or so visitors in the men’s prayer room of Finsbury Park mosque, north London, during an inaugural national open day for Islamic places of worship. “We haven’t got any bombs. Yes, there is a bad history here, but we have changed that. Those people were not representative of Islam.”

By “those people”, Said meant the radical cleric Abu Hamza and his supporters, who seized control of the mosque in the late 1990s and turned it into arguably the UK’s foremost centre for radical Islam, a troubling period that culminated in a massive armed police raid on the building in 2003.

The mosque has since been firmly in mainstream hands, while Hamza spends life in a US prison for terrorism, but it still suffers reputational damage. So it was something of a natural fit for the Visit My Mosque day organised by the Muslim Council of Britain (MCB), which aims to show off the pastoral and community efforts of mosques while also offering reassurance to locals. The MCB said one reason for the open day was to “reach out to fellow Britons following tensions around terrorism”.

Khalid Oumar, a trustee of Finsbury Park mosque, which attracts 2,000 people to Friday prayers, said it had received hate mail after the Islamist-inspired attacks in Paris last month. “One of the reasons we are taking part is the increase in Islamophobic attacks against Muslims,” he said. “Also, specifically, this mosque has a history. We drew a line under that 10 years ago, and there’s a new history of stability and community cohesion.”

The MCB’s website listed just over 20 mosques around England taking part, a tiny proportion of the estimated 1,700-plus nationwide. Others were expected to be involved, however.

Finsbury Park has for several years held its own open day for schools and local people, Oumar said, and was keen to be involved in the MCB initiative. “The object is to show that we’re open, and that we continue to be open. And people are showing a tremendous interest. We’re determined to be out there. We try and do this on a regular basis to make sure that our doors, and our hearts, are open to the community.”

While the first visitors were about one-third media, groups of local people and the curious from further afield continued arriving for guided tours lasting all day.

Said took visitors first to see the women’s prayer room in the basement of the nondescript 1990s building, which has a TV feed to show the imam preaching to the men upstairs. “You might say, ‘Why have you put the sisters in the basement?’” Said told the visitors. It was, he insisted, not sexism, but an arrangement that gave easier access to women with young children.

In his lecture, Said described his doctorate in haematology, a background that explained surprise excursions into grape DNA (to illustrate the wondrous variety of nature), and how fasting for Ramadan can help your body to process glucose properly. Elsewhere in a talk that lasted sufficiently long for the next group to have to stand quietly in a corner while he finished, Said condemned excess corporate profits and recounted Malcolm X’s experiences of the Hajj, the pilgrimage to Mecca.

Anna Louise Oakland, an 67-year-old artist who lives a few streets away, said her first visit to the mosque had allayed some fears. “This place has had some really tricky times,” she said. “I was quite scared for a while, back then. I was thinking, ‘This is not what I want in the area.’ But the more we understand about each other, the more commonalities we find, we can start to let go of our fear.”

Tony and Anna, a couple in their 70s from St John’s Wood, were slightly less impressed. “We learned something, but it could have been more enlightening,” Tony said. While recognising Said was a moderate, he added: “I’m not sure how good he’d be in tempting an impressionable young man away from extremism.”

Two hundred miles away at the Baab-ul-Ilm Islamic centre, host Mohammed Raza Bhani welcomed about 40 people on a bitterly cold afternoon. “Fox News, I hope you’re listening,” he said, to laughter. He explained the purpose of the day – to open the mosque to the north-east Leeds community to “present a more balanced view” of Islam than is often given by the media and politicians.

The centre’s resident scholar, Syed Hadi Hassan, explained how ideas such as forgiveness and caring for others irrespective of creed made violent attacks completely at odds with the core principles of Islam.

The mosque has held regular events open to all communities since opening more than 10 years ago, but Syed Hadi Hassan said they had becoming increasingly significant in light of extremist violence. “In this atmosphere, it is of paramount importance because there are many misconceptions going around. People of the UK are really confused about whether there is something wrong with the teachings of Islam or whether these individuals are using the name of Islam badly.

“We want the world to understand that they are not a part of Muslim Ummah [community] and they are completely alien to Islam and its teachings. It is a beautiful, peaceful religion.”

Syed Hadi Hassan fielded questions on social media on how the concept of jihad has been warped, and when the talks were completed, the visitors were taken on guided tours of the mosque.

“It’s frustrating, but we need to do it and we need to do more,” said Rasool Bhamani, president of the centre. “The problem we’ve got is that the media and politicians talk about radical Islam and Islamic terrorism. What that does is generalise a whole community. By doing that, we’re actually causing divisions in the community and hence, although it’s frustrating, we have to do it to ensure these negative aspects are not associated with the religion.”

Hassan said Baab ul-Ilm worked closely with local synagogues – there is one next door – and churches as part of an inter-faith forum to increase understanding of other religious communities in Leeds.

Jo Hill, 58, a Roman Catholic, said she had heard about the event on the radio and had come to show solidarity with fellow people of faith who were being stigmatised. “I do feel very, very sad. When you see these tragedies happening, it’s not the Muslims. It’s fanatics.”

It was her first visit to a mosque, she said, and more events like it would help increase people’s understanding of Islam. “I don’t think people have any imagination of what the faith is like. I couldn’t even recognise this as a mosque – I went to the building across the road,” she said.

“It’s terrifically important, said Tony Pickles, 66, also a Catholic. “There should be more of this so we can break down barriers and blind prejudice. Some people are ignorant and make judgments and that’s wrong.”

Hill believed attacks like those in Paris increased Muslims’ fear they would be targeted. “My friend says that whenever something happens, she’s abused on the buses into Leeds, and that’s so sad, so to open up like this is a really good idea. It’s terrible because they are just ordinary, God-loving people, and God has nothing to do with the terrorism that’s gone on.”

That sentiment was shared by Helena, who had come along to understand the core principles of Islam. “What came across today was exactly the same as what Jesus Christ taught, which is to love thy neighbour as thyself. It just seems to me that religions are being taken over for political means and the real message is being distorted.”