Many parents dread the school summer holidays, but take a moment to think about the mother heading one of Britain’s biggest families.

Sue Radford has opened up about her "crazy" summer break — with $435 weekly food bills, three hours spent tidying every night and her "military" packing procedure.

The 44-year-old super-mom lives in Morecambe, in Lancashire, England, with husband Noel, 48, and their 21 kids.

"The summer holidays are a bit crazy and, with so many children, it gets very expensive. We don’t save for it, we just have to go with the flow," Radford exclusively told the Sun's Fabulous Digital.

The couple doesn’t claim any benefits apart from the U.K.'s Child Benefit program, and relies on Noel’s bakery business to make ends meet. But Sue has admitted her weekly shopping bill leaps to around $435, when the kids are home from school.

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The Radfords are parents to Chris, 30; Sophie, 25; Chloe, 23; Jack, 22; Daniel, 20; Luke, 18; Millie, 17; Katie, 16; James, 15; Ellie, 14; Aimee, 13; Josh, 12; Max, 11; Tillie, 9; Oscar, 7; Casper, 6; Hallie, 3; Phoebe, 2; Archie 18 months; and Bonnie, 8 months.

They also have three grandchildren — Sophie's kids — named Daisy, 6; Ayprill, 4; and Leo, 2.

"The weekly food [bill] goes up massively during the summer. Normally we’ll spend about $310 a week, but it can go up to $435. For eating out, you're looking at least $185 a time,” Sue said.

The stay-at-home mom lives with her husband and kids in a 10-bed former care home, which they bought for around $300,000 in 2004.

Eldest kids Chris and Sophie have moved out, but all the others are still at home, and it's just as chaotic as you'd imagine.

"The house does get messy. It’s the school holidays, I think you’ve just got the accept that,” Sue said. "I gut the house when the kids go to bed, rather than constantly doing it during the day.”

"You would be constantly cleaning up after them, all day long, otherwise,” she claimed. "It takes two to three hours to clean up after them all, the kids can make an awful lot of mess very quickly.

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"The laundry is non-stop during the school holidays, too. I do about three loads a day in my 40-pound washing machine." (A standard washing machine takes just 15 pounds, so that would be between seven and eight daily washes for many homes.)

With a family twice the size of a soccer team, you might think it's tempting to stay at home during the summer. But the Radfords are determined their kids should have a normal upbringing, and still book family vacations with 21 kids in tow.

Savvy Sue uses labeled bin bags to pack her seven suitcases,so she doesn't get mixed up between the kids.

"We do go away as a family. We went to Florida in February and we're going to Holland this week, but it's a military operation,” the mom said. "The packing process is hard work, but if I put each child’s clothes into a bin bag and label whose it is, it makes it a lot easier when we get there. Then I can get the bags out and put them away, rather than rooting through, trying to figure out whose is whose,” she revealed. "Normally we take about seven suitcases with us."

"We try and do things all together as a family. When the kids are off school, I think it’s nice to spend time together,” Sue said. "Some of the older kids might not want to come or they’ll be at work because they all have different shifts. But we still end up with a lot of children to take out."

With 15 kids at school age or below, one of the biggest challenges is keeping track of the young ones.

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"It can be quite hard to keep track of them. You have to eyes in the back of your head to make sure you don’t lose any children,” she explained. "The older ones are quite good at helping out with the younger ones, we’ve never lost any yet so we’re doing alright I think. They don’t tend to wander off, they’re pretty good.

"Normally, we'll try and do three days out a week during the summer, but we love going for walks, to the park, the beach or going for a picnic with the kids,” Sue shared. “There's a lot of days out that don't require spending money.”

"If I'm doing a packed lunch for everybody, it’s two loaves of bread, three packets of sausage rolls, 24 packets of chips, a bottle of cordial, it’s massive,” she dished. "If it’s really bad weather, we’ll just put a movie on, maybe have some popcorn and do games in the house.

"The kids will fight about wanting to do different things. They're not too bad, but all kids argue and bicker."

The supermom also gave her fans a tour around their enormous home — which has 10 bedrooms but just one bathroom.

This story originally appeared on The Sun. Read more content from The Sun here.