Tributes were paid to David Lomon during the annual Spanish Civil War international brigades commemoration in Jubilee Gardens on Saturday afternoon.
David Lomon was the last surviving UK-based member of the international brigades who fought General Franco's forces in the 1936-1939 conflict. He died in December aged 94.
A year ago he was in Jubilee Gardens to unveil a new plaque set into the paving at the foot of the permanent memorial to the British volunteers who joined the Spanish republican side in the civil war.
On the same day Almudena Cros, representing the Spanish Association of the Friends of the International Brigade, or the 'amigos', presented David Lomon with a Republican flag inscribed with his name.
His son Irving told the large crowd present that his father had often thought about going to Spain to help the Spanish people in their fight against fascism but had not made a final commitment.
"In 1936 the Battle of Cable Street changed everything for him. Being involved in that demonstration was the catalyst. The way that Mosley's fascists were sent packing that day convinced him that he could make a difference."
Other speakers included former union leader Rodney Bickerstaffe, ASLEF general secretary Mick Whelan, Professor Paul Preston and a representative of the Catalan government.
It was announced that an online petition was being launched by the AABI International Brigades friendship group in Spain to save the International Brigades memorial at Madrid's Complutense University. A court had ordered its removal on the grounds that planning permission has not been approved. David Lomon was a guest at the unveiling two years ago.
Music at this year's London commemoration was provided by folk protest singer Grace Petrie, who a week ago appeared to acclaim at the Glastonbury Festival, and the Catalans UK Singers.