Mark Thomas interview: The social-activist comedian talks opera, charity shops, and Nicholas Soames

I want to have as much fun and create as much chaos as I can The mixture of theatre, journalism, activism and stand-up I do is about finding ways to complain about social injustice – whether it's a punk gig on the banks of the Thames or getting hold of ladders to change the letters round on a cinema sign to read "Recognise unions and pay fair wage" [as part of a campaign for Curzon cinema workers, which won them a living wage].

I try to find the good in my enemies It's not unusual to be able to get on with people despite what they are doing being awful. The only person I have met who I considered to be without any redeeming features was [Conservative MP] Nicholas Soames. Back in the 1990s, he was avoiding inheritance tax [on family heirlooms he had been left, using a tax concession available at the time of listing them as open to public inspection] and we found out he had a lovely three-tier mahogany buffet with partially reeded slender balustrade upright supports. We organised hundreds of people to make appointments to see it. Eventually he just paid the tax. He was such a pantomime baddie.

London is becoming a hollowed- out bourgeois yuppie shell There is social cleansing and privatisation of public spaces going on and it changes our rights and what we think we are able to do in public spaces: Paternoster Square – next to St Paul's Cathedral and home of the London Stock Exchange – which is owned by the Oxford Properties Group, is one of six London streets that have been privatised, and have their own private security forces. We have rights enshrined in public spaces – the right to protest, to assemble, to freedom of speech – but all those things go to the wayside in a public street that's privately owned.

People who say online activism doesn't achieve anything are wrong Any online action has an impact: people reading and finding out about stuff is a start in itself. And look at the superinjunction controversy [when sites such as Twitter were used to circumvent rulings that prevented the English press naming high-profile individuals involved in alleged scandals]. That was a great example of social media going nuts and doing something positive. As was the e-petition for the WOW campaign [against welfare cuts], which got 100,000 people to sign and engage in the process.

I fell in love with opera as a way of connecting with my father My dad was a bruiser, an intelligent man who was badly served by the education system. He believed in this working-class idea of self-improvement and discovered a love of opera – to the extent that he took cassettes up on the roofs of building sites to play them, which was incredibly embarrassing for me as a 16-year- old punk. When he developed PCA, a type of Alzheimer's, and I started losing him, I got some opera singers to perform at his bungalow, and for those moments he was back with us, and it was when I felt he was most connected. Now I regard his passion as the beautiful idiosyncrasy of a man who didn't care what others thought.

The corporatisation of charity shops annoys me Oxfam may have been trying to maximise the money it raises when it introduced its designer boutiques, but charity shops are meant to be a way of recycling things within the community. I go to charity shops wherever I'm touring and I prefer little places such as the Trinity Hospice charity shop where, when you go in, there's an element of chaos. I did go through a stage when I'd look for classic Jackie Chan DVDs wherever I went.

Mark Thomas, 52, is a social activist and political comedian. He is touring the UK with his latest show, 'Trespass', from 1 December to 7 May. For venues: markthomasinfo.co.uk