BORIS Johnson's last act as London mayor was to officially open the capital's newest cycle superhighway, a segregated bike path across Blackfriars Bridge.

It was a fitting curtain call for an eight-year tenure which has seen the number of bike journeys grow by two thirds to now record levels, with forecasts predicting that cyclists will outnumber private cars during rush-hour in Central London within the next few years.

Cycling is arguably the former mayor's greatest legacy, both in the popularity of so-called 'Boris bikes' and his spearheading of the cycle superhighways.

As he stepped down, he urged his successor to lobby the Government for transport funding for cycling projects and expressed regret that he had not pushed for segregated cycleways sooner - but conceded the controversy would probably have cost him his job.

He said: "If I had my time again, and if I knew then what I know now, I would have gone straight in with a massive programme of segregated cycle superhighways. I probably wouldn’t have been re-elected, unfortunately. That’s one thing to consider. But that would have been the right thing to do."

The London case encapsulates the struggle facing any leader who decides to put cycle promotion at the top of their agenda. As such it offers a blueprint to city councils in Glasgow and Edinburgh, who must also balance the desires of cyclists and the health and environmental imperatives of making cycling more appealing against the inevitable ire of motorists who resent losing road space to "arrogant", "self-righteous" and "dangerous" cyclists (just some of the adjectives which tend to crop up on the Herald comment board under any article about cycling).

In London, cycling rates have increased from a modal share of 1.2 per cent of all journeys in 2000 to around 4.3 per cent now, or 7.2 per cent within inner London.

However, Transport for London has also admitted that its cycling schemes have played a part in worsening congestion in the capital, with average pan-London journey speeds grinding to an all-time low of 16.5mph. The cycle superhighways were only one of the factors at play though, along with roadworks and 25,000 Uber cabs.

Edinburgh City Council leaders are in the midst of their own proverbial rock and a hard place over the proposed Roseburn-Leith segregated cycleway - the Scottish capital's equivalent of Boris's superhighways.

One particularly contentious stretch around Roseburn Terrace, which would involve reducing parts of a main road already known as a congestion blackspots from four lanes to two, has bitterly split the for and against camps. While local residents and traders hostile to the scheme complain about horrendous congestion and the potential loss of business, those in favour insist detractors are exaggerating and misrepresenting the plans.

As the saying goes, "you can't please all of the people all of the time", and that is rarely truer than when it comes to cycling policy.

Meanwhile, the SNP return to power still "determined" to see 10 per cent of all journeys being made by bike by 2020, from a current baseline of one per cent - a target which even cycling's biggest supporters admit there is now "no hope" of achieving.

Perhaps, like Boris, they wish they had started sooner.