Kashmiri separatist groups and Khalistan sympathisers who tore down the Indian national flag from one of the official flagpoles set up for the 53-nation Commonwealth Heads of Government meeting in London on Wednesday were led by Pakistani-origin British Member of Parliament (MP) Lord Nazir Ahmed.

The British MP, who led the protesters, is known for making anti-India statements in the parliament and racking up the Kashmir issue. According to reports, the MP had hired several open roof tourist buses with signage of "Free Kashmir" and "Modi not welcome" to organise protests around the city.

"The 3 days ride of buses are completely free of charge and paid by his honourable lord Nazir Ahmed. The skies above London will be filled with flying balloons for Kashmir to be seen from across London and streets by convoy of the buses and vans. Good opportunity to get children involvement in a friendly protest manner to high light Kashmir issue to international community by releasing balloons from buses in London (sic),” a London-based Pakistani, Javid Iqbal, had written on Facebook.

India has expressed its concerns to UK authorities at the Foreign and Commonwealth Office, who have reportedly responded apologised for the failure of the police to respond immediately to stop the violent protesters.

"We have expressed our concerns with the British authorities and they have apologised for the incident. We have been warning against some of these elements out to make trouble and they have assured us of action. The Indian flag has now been replaced," a senior Indian official associated with the PMs visit said.

A Metropolitan Police statement said it is investigating the case.

"Police are investigating after an Indian flag in Parliament Square was pulled down at 1500 (UK time) on Wednesday, 18 April. The flag has been replaced. There have been no arrests. Enquiries continue," the statement said.