Jesus came into Galilee, proclaiming the gospel of God, and saying, "The time is fulfilled, and the kingdom of God is at hand." (Mark 1v15)

A few years ago the renowned psychological illusionist Derren Brown pulled off a stunt involving two advertising executives.

He asked the ad men to devise a poster for a hypothetical new business. After they had unveiled their draft, Brown invited them to open a sealed envelope he had given them before they started their design. It contained a sketch he himself had done earlier and which, astonishingly, was virtually identical to theirs.

Brown then revealed that along the route of the taxi ride which the TV company provided to bring the men to the studio, he had set up all sorts of subtle cues – posters, objects, people doing various things – which he hoped would take root in the minds of the advertising execs subconsciously and generate this particular design. The aim was to show how powerful subliminal advertising is.

And it worked. The men's minds had been moulded in ways they never imagined. They came up with almost exactly the result he wanted.

Which leads to the question: who or what is shaping your life? Or, to put it another way, who rules your life? Have you ever stopped to consider the many powers – both conscious and unconscious – that affect you? It's not just advertising, of course. There are politicians and judges, TV presenters and radio hosts, bloggers and newspaper columnists, not to mention friends, relatives and colleagues. Then there are our own hearts – perhaps the most complex and mysterious of all influences. How are we being shaped? Who or what rules us?

It is as we consider such things that Jesus' message sounds as a wake-up call. Almost his first recorded words in Mark's Gospel are the announcement that "The kingdom of God is at hand." In other words, God's rule over people's hearts and lives is now being established – and we are to listen up.

Some have seen the concept of the Kingdom of God as oppressive. In His Dark Materials author Philip Pullman unfolds a story in which God is eradicated and a Republic of Heaven is established. Indeed, Pullman has been quoted as saying: "If there is a God, and he is as the Christians describe him, then he deserves to be put down and rebelled against."

But the arrival of God's Kingdom does not bring oppression; it brings freedom. It is – as the first 15 verses of Mark declare three times – "good news". The coming of the Kingdom is like the liberation of a country which has been locked down under enemy occupation, gripped and shaped by powers beyond its people's comprehension or control – and which is then released from captivity as the forces of freedom sweep in.

The Kingdom of God is not some airy-fairy concept or a vague belief in an afterlife: it is Jesus' invitation to people to pledge themselves to him – to who he is, what he stands for, and all he accomplishes through his cross and resurrection. It's an invitation to be redeemed, renewed and re-shaped in our very core under his liberating rule.

God's Kingdom comes to individuals as they recognise Christ as King – as the one who has a right to determine how we live. Philip Pullman once said: "Maybe there is a God out there. All I know is that if there is, he hasn't shown himself on earth." He has yet to discover who Jesus is – and hence the Kingdom of God baffles him.

Today, as we see an advert, or hear a politician, or listen to a radio presenter, let's choose afresh to submit our hearts to the transforming rule of Jesus Christ. And so we pray: "Your Kingdom come."

The Rough Guide to Discipleship is a fortnightly devotional series. David Baker is a former daily newspaper journalist now working as an Anglican minister in Sussex.