When asked how his first 100 days in office - which falls next week - will be remembered Boris Johnson tilts his head to signal a moment of quiet contemplation.

It has been a lively start.

Knife crime and two high profile resignations - political adviser James McGrath quit in June and deputy mayor Ray Lewis resigned earlier this month- have ensured a challenging beginning to the Johnson term.

But reflecting on his “fantastic and special” job the Mayor of London springs to life, enthusing it is full steam ahead towards his ambition for a "fairer, greener and safer London”.

And keeping youth at the top of his agenda Mr Johnson hinted the widely expected transformation of the London Development agency (LDA) could involve a remit to help the city's young.

Housing pressure

“It has been fantastic. I hope we have done some good things,” he says as we make our way down the Thames by boat from Putney, his trademark blond hair - which is again reassuringly unruly after a mandatory pre-election cut - flapping wildly in the wind.

“We are bringing some really big plans on housing forward in the autumn. “London has a crisis and while building companies are in dire straits the pressure on housing hasn't gone away,” he said.

Knife crime clearly concerns Johnson, and repeating a call for tougher sentences for knife carriers he said the “good work and ideas” of Ray Lewis – who quit amid claims of financial irregularities earlier this month – would continue.

But conceding words from an authority figure like the mayor may hold little sway with some angry youth he acknowledged action was needed from the bottom up - adding the mayor had a wider role to play in changing knife culture.

“It is tragic that kids feel so scared that they carry knives. It is also tragic they feel carrying a knife is glamorous and cool,” Mr Johnson said.

Young people and knives

“It is crazy and risky, and if you carry a knife you increase the risk of it being used.

“How we get that message across to kids is very hard,” he said, adding protecting and reclaiming playing fields for young people to use would help.

“The LDA could also look at the early stages with children . . . the most important skills are reading and writing. The mayor can really organise that,” he said.

“I think the motto for the LDA should be ‘homes, jobs and skills for London’.”

Johnson is also pushing ahead with his green agenda, and when discussing cycling in particular he becomes dangerously animated.

Green agenda

His team is looking at the feasibility of introducing cycle superhighways through London and a cycle “hire” system should be a reality before the Olympics.

“We have to encourage people to feel safe on their bikes and we are looking at having cycle hire stations across London by 2011, like they have in Paris,” he said.

“It is not for a while yet but we are looking for a name for the scheme, maybe you can ask your readers for suggestions?”

Skyscrapers have been a contentious theme, and with several developments at various stages of planning in south London he reiterated his wish to keep tall buildings “in clusters” and only where “local people say they are appropriate”.

Croydon the third city

He also gave the thumbs-up to Croydon’s £3.4billion town centre renovation plan and put his weight behind the borough's bid to become London’s third city.

“I like what they are doing in Croydon, you can't fault it. Croydon is the third city of London, it is going to be.”

He also said the suburbs and zone one would be treated equally - an issue that dogged his predecessor.

“The same issues are affecting the suburbs as zone one, quality of life is affected by rail and other transport links and I shall be working to make things better,” Mr Johnson said.

That commitment will soon be put to the test the mayor tries to secure funding for the second stage of the East London Line extension - linking Clapham Junction and large parts of south London to the Tube network via rail from Surrey Quay, Queen's Road Peckham and a new station at Surrey Canal Road.

More trains and Tube

Funding needs to be secured by September, but, if it can be achieved, the mayor would have a double win of saving £10million in "roll-on costs from phase one" and having the extension built in time for the Olympics.

“We should go for it, we need to get on with it," he said. "We met with [transport secretary] Ruth Kelly and it is a priority; we are pushing very hard.”

And Mr Johnson was also ebullient about another of his favourite topics - Heathrow. “We do not need more expansion at Heathrow, ever.

“I have always been against it. We are looking at the alternative rail links and other airport capacity around London with the possibility of an airport in the Thames Estuary,” Mr Johnson said.

“My own view is that in 20 years’ time rather than have people flying into this county over the principal city and accommodation they should fly into a well linked airport in the Thames Estuary.”

When told that a reporter was not stopped or questioned once when he tested the mayor's alcohol ban on the Tube Mr Johnson bluntly retorted the battle to change attitudes was being won.

“I think it is changing, we are seeing a culture shift and people now know it is not acceptable to drink on tubes and buses,” he said. “People from around the world are amazed that we have allowed it for so long.”

Chocolate bust

And turning from drink to food Mr Johnson also admitted he would be sympathetic to a request from Streatham chocolatier and sculptor, Paul Wayne Gregory, who wants to make a chocolate bust of the mayor to as part of a series highlighting the problem of gun and knife crime in the capital.

"I am sufficiently egotistical for that," Mr Johnson said, “Anything to help London businesses.”

And as our boat reached the pier at Blackfriars the mayor suddenly remembered the reason he was on London’s oldest motorway.

Astounded that we had only passed a few boats on our peak-time journey downriver he extolled on the benefits of one day having an Oyster Card system for passenger craft on the Thames.

“If this was Istanbul or any other European city the river would be bustling with businessmen going to work,” he said.

“Before we didn't get the economics right and the infrastructure and we just didn't have the political will, now we do.”

As he bounced off the boat, the mayor responded quickly to one last question about ambitions for the rest of his term.

“My main goal is to tackle deprivation and inequality that is holding back kids and Londoners,” he said. “And it is my ambition is to have a fairer, greener and safer London.”

Strong words, and while the mayor has flag-waved some exciting policies - some of which come from his predecessor - next week the political honeymoon will be officially over.

Then the quiet moments of contemplation will be fewer as policy detail is revealed and the hard graft towards those ambitions begin.