One of the British participants on the Mavi Marmara included Abdullah Anas  (using his birth name, Boudjema Bounoua ) and his 19 year old son Muhammad.
Anas co-founded the Office of Services (Maktab al-Khidamat, or MAK), the precursor of al Qaeda, with his father and Osama bin Laden, whom he knew personally . He also helped to start a group that sent jihadis to fight in Bosnia & Herzgovina . He then ran an MAK branch that funded this activity. He sits on the Council in Exile of Algeria's FIS.
Anas is the son-in-law of Sheikh Abdullah Yussuf Azzam, Osama bin Laden's mentor. Azzam co-founded MAK (see above) and helped to start Hamas . Azzam adhered to the bloodiest end of Islamic extremism; his slogan was "Jihad and the rifle alone: no negotiations, no conferences, no dialogs.". Aside from bin Laden, Azzam supervised the PhD thesis of Mullah Krekar (who later led the Kurdish terror group Ansar al-Islam). He believed in the "defense of Muslim lands"; not even a handspan of land that was ever controlled by Muslims must be allowed to remain in the hands of infidels. Unlike bin Laden, who had other priorities, Azzam wanted to focus on destroying Israel.
Azzam's daughter Sumayya (Anas' wife, Muhamad Bounoua's mother) is herself an extremist. She has expressed a willingness to sacrifice Anas and all of her 5 children for Allah. Anas brought his 19 year old son Muhammad on the Mavi Marmara. His 17 year old son Ahmed now wants to join the next convoy. Sumayya supports this, naturally, now that she sees what a wonderful career opportunity it represents: instant credentials in the jihad business.
This "peace activist" family reside in the UK, which granted them political asylum. I'm not sure if this happened as a result of Anas' participation in the FIS or whether it happened because Anas gave reports critical of bin Laden. However, Anas is said to maintain close links with the Taliban and al Qaeda.
Azzam was assassinated in Pakistan, though who killed him is a mystery. His death gave bin Laden control of MAK.