The Pilgrims didn't only risk their lives at sea to reach America; many of them left everything they had to start a new life living according to their religious beliefs.

The Mayflower carrying the Pilgrims to America set sail from Plymouth, England, on 16 September 1620 according to today's Gregorian calendar - 6 September in the Julian calendar they used at the time.  

In a discussion hosted by the Religion and Media Centre, historian Francis J Bremer described how many of the Puritan leaders left positions of influence and affluence in England to follow their religious beliefs, first in Leiden in the Netherlands for 10 years, before departing for the New World. 

When the Mayflower left Plymouth in 1620, it was carrying 30 crew and 103 passengers, nearly half of whom were separatists. Forty-five of the passengers would die in the first harsh winter in the New World.

One of the passengers onboard was William Brewster, who had lived in the manor house at Scrooby, Nottinghamshire, a building described in contemporary accounts as being very grand.  While still in England, he inherited his father's positions of Master of the Queen's Posts and bailiff, but left it all and went on to became an important leader in the new Plymouth colony. 

"By becoming a separatist, he loses that and in Leiden basically lives in a one-and-a-half room house for 10 years, and then comes to America and builds his own small shelter," said Bremer, who is the author of a new book on the Plymouth Puritans, One Small Candle.

"So the luxuries that they are willing to give up, the benefits of life in England that they are giving up, I think the easiest explanation is religious." 

While some people heading out to the new colonies were hoping for material gain, Bramer said the Pilgrims sailing on the Mayflower were "not interested in making a quick buck". 

"With everyone coming to America at this point, this is incredibly dangerous. The first winter in Plymouth, half of the colonists died ... so you're taking enormous risks," he said. 

"For most of the people doing this, they're making an irrevocable decision.  In order to finance your journey to the New World, you have to sell your English land, you have to sell whatever other assets you have, and you get to America and if it doesnt work out you're stuck, because if you're in a failing American colony, you can't finance your way back home by getting someone else to buy what you have in America because it's worthless.

"Did some people hope to benefit financially from this or at least to live comfortable lives? Yes, there is some economic aspect. There is also a social aspect. A lot of people are going because their families and members of their congregation are going.

"But primarily this is driven by a religious social outlook and a desire to live the way they feel God wanted them to." 

Historian Rebecca Fraser agreed that the impetus for making the arduous journey across the Atlantic was first and foremost religious. 

"If you go to East Anglia, where something like 40 per cent of the early inhabitants of New England came from, a huge amount of the leaders came from manor houses [and] beautiful homes, so they really were giving up a huge amount for a godly society," she said. 

"John Winthrop [a Puritan and one of the founders of the Massachusetts Bay Colony] had a really beautiful manor house.  If you read accounts of the early settlers, whoever they were, even if they were the Earl of Lincoln's daughter, you arrived [in the New World] and basically the houses were not ready for you.

"And so many people died even founding Boston 10 years after the Mayflower.  Even though the Pilgrims were there to help them, the mortality rate was staggering.

"The impulse is really religious because they are giving up so much in their former home country." 

This year marks the 400th anniversary of the Mayflower and events are taking place on both sides of the Atlantic to commemorate the event. 

Bremer said it was important to remember that it is a part of both American and British history. 

"This is a transatlantic movement," he said.  "This is not just an American story; it's an English story." 

Journalist Jonathan Petre, whose family home has ties to the Puritan settlers, said the Mayflower history was "under-taught" in Britain.

"I don't think it's very well taught in this country - and the impact it had on America," he said.