I think it started long before that, in all truth.
Councils have quietly been making cuts for decades. It started when Thatcher told everyone that they could pay less tax and still have the same services. (The gap would be filled by 'efficiencies.') Frankly, if you believed that you were singularly naive. In any case, one man's 'efficiency' is another man's 'cut'.
Councils started by cutting stuff people didn't see. Like baiting sewers with rat poison. That was cut right back, which is why we now have 100,000,000,000 rats. (Real ones, not the ones in rag shirts.) But no one minded at the time. Then they started cutting back on drainage work, sewer maintenance and gully cleaning. No one minded at the time, because it had no immediate impact that the public could see.
It's only in comparatively recent years that they've been forced to cut things that people can see. Like libraries and school budgets. Because they protected these for as long as they could.
This has had a cumulative effect. But the truth is, we've underinvested in sewers, drains and their maintenance for decades, and with the shitty weather we have now you're beginning to see the consequences. And even now, no party will put at the top of their manifesto 'We will spend billions upgrading sewers and drains.' Because it's not a public priority. Well, only for those who get flooded out, and then only for a few months.