Progressive jackpot slots have been around for a few decades now. They award a pooled prize, or share of one, to a lucky player gambling on a network of machines.

But as the number of online slot games have increased, and more players take to the casinos, the jackpots have grown and grown. Let's take a look at five of the biggest video slot jackpots ever...

1. The soldier who came home a winner

When: 2015

Amount won: £13.2m

Where: Betway Casino

Game: Mega Moolah

In 2015, the record for an online slot jackpot was broken when former soldier Jon Heywood took down the big one on Mega Moolah.

The 26-year-old was playing at 25p coins when he triggered the Mega jackpot for a staggering £13.2m. When converted to Euros, the prize pot just beat out the previous record held by Mega Fortune.

The jungle-themed slot features four levels of progressive jackpot, with the top Mega jackpot seeding at £1m. However, with the lowest Mini jackpot seeding at 10.00, even lower-stakes gamblers can pick up a prize.

Amazingly, Mega Moolah paid out over €4.5m in 2017 alone. What are the chances of Jon's win being beaten in 2018?

2. Mega Fortune takes the record

When: 2013

Amount won: €17.8m

Where: Online

Game: Mega Fortune

Before Jon Heywood took down his Mega Moolah jackpot, NetEnt's Mega Fortune slot held several world records for online progressive jackpots. And in 2013, an unknown Finnish gambler won €17,861,813 on the money-themed slot.

The anonymous winner was reported to be a mature student, but under Finnish law he was possibly due a hefty tax bill.

Mega Fortune records obviously go in cycles. The previous record for its online progressive jackpot came in 2011 when a Norwegian student won €11.7m playing the game.

Like Mega Moolah, Mega Fortune features several levels of progressive jackpot, each seeded at a different amount. Two are "local" to the game - the 'Rapid', which starts at €50, and the Major at €5,000. The Mega Jackpot is pooled across all participating casinos and can easily reach an expected value of €4m.

3. Megabucks pays out again

When: 2003

Amount won: $38.7m

Where: Excalibur, Las Vegas

Game: Megabucks

IGT's land-based Megabucks video slot has been creating millionaires since the mid-1980s. Although Megabucks slot themes can vary, many branded machines are linked across multiple casinos. As with online casinos, this can mean only one thing: massive payouts.

In 2003, a young software engineer deposited three $1 coins in the Megabucks video slot at Las Vegas' Excalibur casino. He hit the top payline to win a jackpot that has odds of 49,836,032/1 of winning.

Megabucks jackpots are generally paid out over 25 years. But even with the IRS taking a healthy slice of US income tax off the top, the engineer will still be set up for the rest of his life.

4. The two-time Megabucks winner

When: 1989 and 1995

Amount won: $4.6m and $21 million

Where: Mirage, Las Vegas and Cannery Casino, Las Vegas

GAME: Megabucks

The odds of landing one Megabucks jackpot are close to 50,000,000/1. The odds of hitting two just broke our calculator. But that's what one lucky American gambler achieved over a six-year period.

Elmer Sherwin managed to win $4.6m at the newly-opened Mirage casino in Las Vegas in 1989. Incredibly, just six years later and now 92 years of age, Sherwin won the IGT linked jackpot again. The Cannery Casino & Hotel was the World War II veteran's place of choice that time around. And on the second occasion, Sherwin won $21.1m.

Famously, the double winner donated a large portion of his winnings to help the victims of Hurricane Katrina. But time waits for no-one, not even slots millionaires, and two years after his second win, Sherwin passed away.

5. Mobile casino games get in on the act

When: 2017

Amount won: €8,012,153.35

Where: Online

Game: Mega Moolah

It's not just online and in land-based casinos that players win life-changing amounts of cash. Increasingly, mobile casinos are dishing out six-figure jackpots, too.

A few years ago, a Canadian player won what was at the time the biggest ever mobile jackpot. The anonymous player's C$7.5m win on The Dark Knight (USC$6.02m) didn’t quite match the sums seen by The Dark Knight's sister slot, Mega Moolah, but it showed how far mobile casino slots had come in such a short space of time.

More recently, Mega Moolah players have enjoyed success on their smartphones. In 2017, a Mega Moolah gambler snatched the game's Mega jackpot for just over €8m, the largest mobile jackpot win in history.

Like all Microgaming progressive slot jackpots, the sum was paid out in one lump sum.