[4][5][6] They are the first member of the Electrostar family, which also includes Classes 375, 376, 377, 378, 379 and 387, and are the most numerous type of EMU built in the post-privatisation period of Britain's railways.

It consists of an underframe, which is created by seam-welding a number of aluminium alloy extrusions, upon which bodyside panels are mounted followed by a single piece roof, again made from extruded sections.

There are also LED displays inside, at the end of each carriage above the gangway which give route and customer service information.

Prism Rail was purchased by National Express in September 2000, and the franchise was rebranded as c2c once the Class 357/0 units were in service.

In June 2001, units 357025 and 357027 had vinyl stickers applied with two prototype variants of the proposed purplish blue and magenta c2c livery at Bombardier's Derby Litchurch Lane Works.

Hence, although the underlying paintwork and interiors of the two sub-classes were different when delivered, their exterior appearance is identical, and the only way to distinguish them externally is by their numbering.

When the Quiet Zone car was introduced in each set, this was marked on the exterior of the doors by a magenta and white sticker.

On 19 April 2004, the unusually large rate of increase in atmospheric pressure led to an airlock and failure of hydraulic pressure on eight of the Class 357 trains which caused their computer's software to lower their pantographs and so be unable to collect power from the overhead lines, causing service disruption.

[9][17] After their technical problems were sorted out, they have since been the most reliable fleet of EMUs in the United Kingdom,[18] winning Best Modern Era EMU at the Golden Spanners Awards from 2005 to 2007, for an average annual miles per casualty (MPC) figure of 43,180 in 2005,[19][20] 37,391 in 2006,[21] and 45,459 in 2007[22] (defined as the number of miles a train runs before a defect develops causing 5 minutes or longer delay).

In December 2005, c2c's East Ham depot began putting advertising vinyl wraps on some carriages, starting with branding the MSO intermediate trailer car 74716 in set 357216 as a 'Cough-Free Zone' by the cough syrup makers Benylin for the winter.

[citation needed] After repair at Derby Litchurch Lane Works, 357203 was repainted and re-entered service on 30 July 2009.

Similar work was carried out on the rest of the fleet over the next 21 months at Bombardier's Ilford Depot, where the units were repainted into their original white colour, but with dark blue doors, and branded with both "national express" and "c2c" logos in lower-case.

[29] In March 2023, unit 357016 was unveiled in a special livery for a partnership with the British Transport Police, to publicise their new App "Railway Guardian".

The blue livery features QR codes leading customers to download the new app in order to help improve the safety for passengers travelling on the railway.

[31] In March 2007, 357028 returned from the Czech Republic, having gained safety certification, and c2c began fitting the regenerative braking systems to the rest of its Class 357 fleet, becoming the first UK train operator to do so.

The units were generally used on London Liverpool Street to Southend Victoria services on the Great Eastern Main Line (GEML).

The system consisted of six television screens and ten speakers in each carriage, and was also intended to be used to deliver real-time travel information.

In June 2006 the '360 On-Board Television' service ran into financial difficulties when c2c's partners in the project, TNCI (UK), ceased trading, and the equipment was removed.

[42] In October 2007, c2c announced that the country-end carriage of each unit (i.e. Shoeburyness end of the trains) would be made into a "Quiet Zone", where the use of mobile phones and personal audio players is prohibited.

[43] A trial was carried out to install special film onto the windows of the Quiet Zone carriages to block all mobile phone and Wi-Fi signals.

[citation needed] On 5 November 2006 at about 00:30, 357043 hit a red Ford Escort which had come off the road and crashed through a boundary fence onto the railway line.

A nameplate is placed above the leading carriage's foremost passenger window between the cab door and the air intake on either side.