Google's global headquarters has the uncanny feel of a carnival. Beneath cloudless California skies, engineers in board shorts glide through the leafy campus on brightly coloured bicycles.

Step inside and find a cavalcade of attractions: giant stuffed animals and a VW camper van are parked up in the corridors beneath signs advertising belly dancing and K-Pop classes.

In the distance, a colossal tent-like structure resembling a circus Big Top is under construction, which once complete in 2021 will be the company's new HQ.

Amid all this excitement — and with gushing profits of over US$15 billion ($23.95b) in the first six months of this year — there should be plenty to smile about for Google's ringmaster in chief.

But Sundar Pichai, 47, is in a sombre mood. Seated in a first-floor meeting room overlooking Silicon Valley, the search giant's chief executive admits the pressures of the job sometimes get to him.

"I don't sleep well when we get things wrong," he says. "When we make a mistake it's obvious to the world. So it's something I feel."

A lanky south Indian who joined Google in 2004 and has served as chief executive since 2015, these days Pichai has plenty to keep him up at night.

Since its creation in 1998 by Larry Page and Sergey Brin, PhD students at nearby Stanford University, Google has unleashed a blizzard of products on the world that have transformed the way we live — from its eponymous search engine to Gmail, Google Maps, the Android operating system and its Google Chrome browser.

As a business, Google has become a formidable machine, generating colossal profits and turning Page and Brin into two of the world's richest men with a simple formula: hoovering up oodles of data on users and serving them up highly relevant ads. But as Google turns 21, the mood in Mountain View has darkened. It is Pichai who finds himself carrying the can.

Besieged by concerns about toxic content, data privacy, tax and the use of Google's YouTube service by paedophiles and extremists, Pichai finds himself in a maelstrom of controversy over the role Big Tech companies play in society — and a battle with regulators over how to rein them in. He sets out the complex juggling act Google faces trying to keep up.

"We've been operating as a company for 20 years selling products for billions of users across many countries — and laws and regulations are evolving," he says.

"Sometimes the products and use cases evolve much faster, and we're in the middle of trying to make it work."

As a father of two, how does he feel about children viewing toxic content on YouTube?

"Many of us are parents," he says. "We deeply care about children's safety and privacy."

As a software engineer, he sees the solution in improved technology to spot and remove malign content.

"The toughest problem is not everyone agrees sometimes what is problematic content, and that's hard."

Google's sheer commercial heft is becoming a growing political problem too. With a 37 per cent share of the global digital advertising market, critics have long complained that Google — whose parent Alphabet, with a market value of US$858b is the world's fourth biggest company after Microsoft, Apple and Amazon — is simply too big.

Google employees march out of their offices to join others in a climate rally in San Francisco. Photo / AP

The European Commission's competition chief Margrethe Vestager has already levied fines on the company worth US$9.3b, but this month the pressure intensified on both sides of the Atlantic. Not only did Brussels reappoint Vestager to a new and enhanced role designed to take on Big Tech, but attorneys-general from 50 US states launched an investigation into Google's dominance in both search and advertising.

The mild-mannered Pichai, who was paid US$1.8 million last year and has a fortune of more than US$1b, offers a measured response but treads carefully. "It's fair that governments, which have a charter to protect their citizens, are thinking about what is the best way to approach that ... So there's going to be important regulations that need to happen in technology, like you've had in other industries."

How would he respond in the event of an ordered breakup of Google — a proposal made by US presidential hopeful senator Elizabeth Warren?

Pichai swerves the question, saying it's not for Google itself to determine whether it has become too large.

"It's a societal level conversation," he says. "Should a company be this big or not — it's not for us to decide. What I can do is make sure we are working hard to build products that improve people's lives."

However, Pichai does offer a spirited defence of the benefits of being a big company, which employs 107,000 people globally and shelled out US$16b on research and development in 2017, or 15 per cent of revenue.

"As a company we have hundreds of researchers who work on AI in healthcare to help better detect and treat diseases, or the work we do on cyber security or threats around deep fakes."

Perhaps it's this deep engineering background that makes him favour clearer rules for how tech companies should operate.

As Google turns 21, the web giant is under scrutiny as never before. Photo / AP

He praises Europe's new General Data Protection Regulation data privacy laws, for example. "In Europe there is a clear framework for privacy so that users have certainty about how their privacy is protected. Companies have clarity about how they can build products and safeguard user data. Hopefully it's a template for the rest of the world."

With his thoughtful manner and low-key style, Pichai is in some ways the antithesis of the flashy Silicon Valley tech tycoon.

A strict vegetarian with a fondness for tea and long walks, he maintains a spartan office and lives with his wife and two children in what has been described as a "shockingly modest" home in nearby Los Altos.

Google's chief executive hasn't received an equity award in two years because he turned down a big, new grant of options last year.

The reason? He felt he was already paid too generously.

Google's unofficial motto has long been the simple phrase "don't be evil", and more than any other company it has maintained a reputation for high ethical standards and liberal ideals.

There have been times recently when that legacy has felt like a burden.

Plans to build a censored search engine for China — where its regular service was blocked by Beijing in 2010 — were dropped following criticism and an internal revolt by employees.

But Pichai says he remains proud of Google's "strong ethical foundation".

"We still use 'don't be evil'," he says.

"It was always an unofficial expression that we used internally at Google and we still use it today. And we always approach our work with a set of ethical standards. Given the scale at which technology works, I don't see any other way."

Finland Prime Minister Antti Rinne, right, and Google CEO Sundar Pichai. Photo / AP

Does he ever worry about the future or the implications of some of the technology the company develops?

Pichai pauses to consider his answer. It's important, he says, to design technology "in a way which doesn't detract from the human experience and adds to the humanity of how things need to work".

"I do worry about making sure when we're building technology, you're bringing everyone along. I worry about a future that may not have equal access to technology and its benefits for everyone."

Nevertheless, Pichai says he remains an unavowed optimist.

"Technology made a difference in my life and I see evidence of that today across our products. We need to be responsible about how we deal with technology, but it will be a big driver of future growth and prosperity and we all need to work hard to make sure it benefits everyone."

From Chennai to Silicon Valley

Sundar Pichai's journey to the top of Google was a long one.

He grew up in Chennai — the baking hot port city formerly known as Madras, which is capital of India's southern province of Tamil Nadu.

Born into a middle class family of Tamil Brahmins — the caste from which Hindu priests are drawn, which traditionally places a high value on education and knowledge — his father was an electrical engineer with British conglomerate GEC, while his mother was a stenographer.

Although a relatively small community, Tamil Brahmins have had an outsized impact, particularly in the world of business. Indra Nooyi, the former chief executive of PepsiCo, and Natarajan Chandrase-karan, chairman of Tata Sons, both share the same background.

Sundar Pichai grew up in Chennai, India. Photo / Getty Images

In India, where Pichai is considered a megastar in the mould of cricket legend Sachin Tendulkar or Bollywood actor Shahrukh Khan, his career trajectory has a dreamlike quality.

After excelling in school, he won a scholarship to Stanford University, then got an MBA at the Wharton School of the University of Pennsylvania.

He joined Google in 2004, the year of the company's initial public offering, after a stint at McKinsey.

A natural engineer, Pichai worked his way up through the ranks, assisting on the development of Google's Chrome browser and a string of other projects at the technology and search giant.

He was appointed as Google's chief executive in August 2015 after previously being named product chief by founder Larry Page.

When he got the job of chief executive, his mother's reaction was predictable: "She wanted to make sure I took care of my health and had enough time to spend with my family."

Telegraph Group Ltd