Aid worker Mr Haines, 44, was the first Briton beheaded in Islamic State videos featuring Londoner Mohammed Emwazi, known as “Jihadi John”, who was killed in a US air strike in Syria in November. Mr Haines’ brother Mike said: “We have been devastated by my brother’s loss and know that other families have been affected in the same way. I would say to them, come and join us, be part of this memorial.