A rail operator has signed a £100 million deal for new trains, adding more seats and capacity for passengers amid expectations of future growth.

c2c, which runs services between London's Fenchurch Street and Southend, said 60 Aventra carriages will be built at Bombardier's factory in Derby.

The new fleet will add almost 20% more seats and capacity from the summer of 2021, three years earlier than previously planned.

The delivery programme has been accelerated following the acquisition of c2c by Italian rail giant Trenitalia earlier this year.

The Rail, Maritime and Transport union (RMT) said the announcement was a victory for workers in Derby who had campaigned to secure a future for train building in the UK.

Each new train will operate in a fixed set of 10 carriages, and will include more than 900 seats, air-conditioning, Wi-Fi, plug sockets and three toilets.

Each new Aventra carriage will be five metres longer than c2c's current Class 357 Electrostars, and will provide capacity for 15% more passengers.

Trenitalia UK managing director Ernesto Sicilia said: "We are delighted to announce this deal, which demonstrates our focus on long-term investments in the UK market and our desire to constantly improve the standing of our trains and to deliver visible and valuable improvements on our services.

"Since our entrance in the UK market the original new trains' investment plan, which included a phased delivery until 2024, has been accelerated overall and we are extremely proud that the new fleet will start to be delivered from summer 2021, three years earlier than what was originally planned."

Richard Hunter, UK managing director of Bombardier Transportation, said: "Our modern Aventra trains are proving ever more popular and this order will help transform the travel experience for c2c passengers and deliver 20% more seats to c2c's fleet.

"It's yet another endorsement of our workforce and the quality of the products we design, engineer, manufacture and service in the UK."

Mick Cash, leader of the RMT, said: "This is a victory for the workforce who have fought and battled through years of uncertainty to secure a future for train building in Britain, the nation that gave the railways to the world."

Rail minister Paul Maynard said: "We are making the biggest investment in the railways since Victorian times to meet the growing demand for rail travel and improve both journey times and passenger comfort.

"These British-built Bombardier trains, which are coming into service earlier than planned, will provide much needed extra capacity for thousands of passengers across London and Essex, and also come with facilities such as Wi-Fi, air-conditioning and plug sockets."