At least 4,000 police officers were called in to stop violence and hate speech on the streets of central London today, as two rival marches took place , resulting in at least 31 arrests. The mammoth security operation , described as "unprecedented" in recent years, cost a staggering £4.5million and included more than 600 cops brought in from around the country to keep Tommy Robinson supporters and Nakba Day marchers apart. Specialist armed officers, large numbers of officers equipped with riot