The uncertain political climate seemed to spell disaster for the business world, but Britain's private companies are holding firm under the threat of a looming Brexit. In fact, according to this year's Sunday Times HSBC Top Track 100, many companies are actually recording their biggest sales and profits ever. From centuries-old businesses to those that have only started in the last 20 years, find out who's leading the pack right now.

Healthcare at Home provides home care and medicine delivery for over one million people each year. A growing patient base saw turnover rise by 11% in 2017, and profits reach a healthy £19 million.

Home Bargains has over 400 stores in the UK, selling a variety of value homeware items. The chain, which employs over 18,000 people, is on an aggressive expansion drive, looking to acquire new stores and build on its growing profits. It's working so far, with the company rising four places in the rankings since last year.

Arcadia is Sir Philip Green's high street fashion empire (he's pictured here with his daughter Chloe, left, and supermodel Kate Moss, right). The group owns the likes of TopShop, Dorothy Perkins, Miss Selfridge and Burton and has 2,600 stores globally. However, a tough retail market in 2017 saw sales drop by 7%, and it has fallen in the rankings from 24 to 28.

Rubix is a freshly-formed hybrid company. The merger between two industrial supplier companies – French IPH and UK-based Brammer – was orchestrated by American private equity firm Advent International. The deal took place last year, and the company was rebranded to Rubix in June 2018 under the guidance of recently-appointed Danish CEO Martin Gaarn Thomsen (pictured). As a result, the firm has leapt a whopping 60 places up the rankings this year.

One-time catalogue shopping business Shop Direct went solely online in 2015, with its successful brands including Very.co.uk and Littlewoods.com. This digital-only strategy has pumped up sales by 6% in 2017. So the future looks even brighter for twins Sir David and Frederick Barclay (pictured when they received their knighthoods in 2000), who own the internet retail business together.

The construction project management company Mace has projects all over the world, from Vietnam's 1,513-foot tallest building Landmark 81 to the current revitalisation of London's Battersea Power Station.

The Reading-based water and waste service company provides 15 million people in London and the Thames Valley with water. In the past year it has seen several new investors come on board, including Canada's largest pension fund OMERS, and the Kuwait Investment Authority. These deals combined were worth £1.35 billion in return for a 26% share of the business.

The fuel card provider, whose cards enable fleet operators to buy three billion litres of diesel a year, saw its sales rise by 15% in 2017. The company is led by founder and chief executive Bill Holmes (pictured) and is set to move to new headquarters, but still in the town of Crewe, in late 2018.

Sir Peter Rigby (pictured left with then-Prime Minister Gordon Brown in 2009) set up the group in 1974, which has its roots in IT, namely services business SCC. The conglomerate now has businesses across many sectors including hotels, real estate and airports, and saw its turnover rise by 21% in 2017.

Joe Hemani (pictured) founded IT product and service distributor Westcoast in 1984. Supplying customers across the UK and Europe, the group's French acquisition Adveo Digital Systems (ADS) France, which it bought in 2016, has boosted the company's turnover by 16% and helped it to rise in the rankings.

The online bookmaker has jumped 10 places since last year, with a 38% increase in turnover and profits up by 10% to £557 million. The reason? The drop in sterling's value, and the 2016 European Football Championships leading to more bets. The bookmaker is owned by the Coates family, with Peter Coates at the helm, who is also a majority shareholder and chairman of his passion project Stoke City Football Club.

The Marshall Group has had a record year in terms of sales. The family conglomerate – now led by Robert Marshall (pictured right, with his father Sir Michael Marshall) – runs car dealership Marshall Motor Holdings, which generated 86% of the group's total revenue in 2017, which was up 15% to a whopping £2.6 billion.

The masterminds behind the partly optician-owned Specsavers stores are Dame Mary and Doug Perkins, who started the brand in 1984 from their Guernsey home. Now Specsavers is a global brand with nearly 2,000 stores across the UK, Europe, Australia and New Zealand, with Canada set to follow.

JCB, founded in 1945 by Joseph Bamford, is still going from strength to strength. Led by its chairman Lord Anthony Bamford (pictured with his wife Lady Carole Bamford), the construction machinery manufacturer unveiled its first electric excavator in March 2018, which produces zero emissions. The business also employed a further 600 people in the first half of this year, reflecting the growing demand for JCB products.

Founded by Sir Richard Branson (pictured) in 1984, airline Virgin Atlantic experienced some difficulty in 2017 and sales dropped by 1% due to the weak pound against the dollar. Dropping two places in the rankings, Branson is set to sell 31% of his share to Air France-KLM in 2019, which will leave him with 20% of the business.

Heathrow Airport is the second busiest in the world, welcoming 78 million passengers in 2017. It's down four places on last year, but in 2017 the airport invested £687 million upgrading its passenger infrastructure, as well as the high levels of freight that it welcomes. In June 2018 MPs gave the green light to Heathrow's much-contested third runway, which will cost £14 billion and is due to be operational by 2026.

Laing O'Rourke is the international engineering, construction and asset management group behind London's 'cheesegrater' tower (pictured), Heathrow Terminal 5 and Hinkley Point C, the UK's first nuclear power station built for a generation. In 2017 the company had a fantastic year, turning the previous year's £18 million of losses into £78 million profit.

The budget food chain was famously started by Sir Malcolm Walker with just £30. He began selling loose frozen foods from his store in Oswestry, Shropshire while working a day job at Woolworths. The business now stretches to 884 stores, and has a very modern approach. It is the first major UK supermarket to commit to removing palm oil from all its own-brand products by the end of 2018 and, going one step further, plastic packaging by 2023.

The metal recycling group is up 11 places on 2017. The company has been salvaging metal from industry, end of life vehicles, construction and demolition since the 1940s, and every year recycles 10 million tonnes of metal at 170 sites across the world. Sales rose to £3.1 billion in 2017 due to the increasing demand for metal.

2 Sisters Food group is a food manufacturer that supplies all the main UK supermarkets from Asda to Marks & Spencer. The company is known for its poultry, a part of the business which made up two-thirds of its £3.29 billion sales last year. 2 Sisters Food Group also owns brands such as Fox's Biscuits and Holland's Pies, and has undergone a period of restructuring, selling off Goodfella's pizzas this April.

A single grocery shop in 1963 has transformed into a conglomerate that owns not only Britain's largest privately-owned cash-and-carry business but nearly 800 Well Pharmacy sites, a cement manufacturing business, real estate, and a bank in Pakistan. And the growth is set to continue. Bestway Group has recently bought up £7 million-worth of drinks distributor Conviviality's brands, as well as starting a van sales business.

Sir James Dyson's company began by reinventing the vacuum cleaner. But now the company is in the midst of a £2.5 billion investment into electric vehicles, AI, and battery technology. Sales in 2017 increased by 40% due to a growing market in Asia, with profits up by 27%. Read James Dyson's story here

Pentland Group owns brands such as Speedo, Hunter, Canterbury and Berghaus. Based in London, the group also owns a majority stake in JD Sports, which bought US retailer Finish Line for $558 million (£417m) in June.

Sir Arnold Clark started his car dealership in 1954 with just one Glasgow showroom. The founder (pictured) passed away last year, leaving a business of 200 car dealerships across the UK that is set to grow. The group's managing director Eddie Hawthorne announced that it is going to recruit 300 apprentices in the UK.

MFG – Motor Fuel Group – acquired distributer MRH, the UK’s largest petrol station and convenience retail operator, in June 2018 for £1.2 billion. The deal is yet to be finally approved by the Competition and Markets Authority, but if it goes ahead it will make MFG the UK's largest forecourt operator in terms of sites with 900.

EG Group is led by brothers Zuber and Mohsin Issa, who started their business with just a single petrol station in 2001. Now EG manages 4,500 garage forecourts across Europe and America. The Blackburn-based company completed a merger with European Forecourt Retail in 2016, and since 2017 has started buying up even more forecourts, with 1,146 in Italy, a further 1,000 in Germany, and 762 in America.

Down one place since 2017, employee-owned John Lewis Partnership – consisting of its two divisions, John Lewis and Waitrose – has suffered due to rising prices and lower demand. The company's chairman Sir Charlie Mayfield blames Brexit, and expects even lower profits in 2018 as the uncertainty continues. The annual bonus for the firm's employees has been cut to 5% of salary, its lowest level since 1954.

The Swire family business has fingers in many pies. From Coca-Cola franchises to property to shipping liners, the company that started as an import and export business in Liverpool in 1816 has become a conglomerate that operates across multiple sectors. In 2017 sales increased by 31%, which was partly down to Swire expanding its Coca-Cola bottling operations in China and America.

What began as a start-up in a bedroom in 1992 has grown monumentally to become the UK's only national fuel supplier. The business received further investment last year and has expanded its work into Canada and Ireland, as well as bolstering its offerings in Brazil and the Middle East. For those who have never heard of Greenergy, the company is set to supply fuel to 80 Esso forecourts this year under a deal agreed in January 2018 with Motor Fuel Group, which is at number 6 in the rankings.

The petrochemical manufacturer INEOS remains in the top spot for the fourth year in a row with £26.9 billion in sales. One of the world's largest chemicals manufacturers, founded by Britain's current richest man Sir Jim Ratcliffe, it specialises in buying up loss-making assets and making them profitable, which began when it bought BP's chemicals division in 1998. The business also owns motorcycle brand Belstaff and Swiss football club Lausanne-Sport.