They were better prepared than in Notting Hill in the 70s (the old pictures of coppers with dustbin lids always vividly illustrate the absolute lack of readiness / training / equipment at that time) but there were very few shield equipped units (primarily the SPG) with an immediate response capability and the back-up serials (a) took forever to call out and deploy and (b) consisted of many officers who had never used a shield before.
Over the next few years that changed dramatically and since then most forces (certainly those in metropolitan areas) have maintained numbers of trained and equipped officers able to respond swiftly (the TSG in London, along with a much larger second level of response, properly trained and equipped, with a much swifter mobilisation plan from divisional duties).
The key in dealing with such disorder is to get more officers there to quell things quicker than the rioters can get help there to escalate it - in the 80s the police were coming second, since then (even with internet and other communications), they usually come first.