The detainee has been identified as 37-year-old Richard Evans.

Evans is the son of Lee Evans, who is the owner of the Rhondda Cynon Taff company whose van was used in Monday's attack, BBC reported.

In his post, Richard wrote, "Glad I'm not running the van hire the police wouldn't like what my answer would be."

"It's my dad's company I don't get involved it's a shame they don't hire out steam rollers or tanks could have done a tidy job then," the post read.

Police said that they detained him for writing hostile material capable of stirring a tension.

However, his father Lee Evans condemned his son's comments and said in a statement, "I want to condemn in the strongest possible terms these ill-considered Twitter comments, which in no way reflect my own view or indeed those of anyone else in the family."

The senior Evans also condoled the loss and said he's cooperating with the police in their enquiries.

"The attack in Finsbury Park was shocking and cowardly. Together with all the staff at Pontyclun Van Hire, I am doing everything I can to assist the Metropolitan Police in their inquiries,' he said.

The Metropolitan Police have already arrested a man from Cardiff, Darren Osbourne, for ploughing through worshippers outside the mosque.

Following the incident, Osbourne's family too expressed shock and condemned his actions while condoling the loss.

Van image: pontyclunvanhire.co.uk