All three towers now stand over half of their final 210 metre height with the deck now emerging from each tower.

This spring the public will see the cables emerge as the towers continue to reach for the skies and the decks widen across the Forth from each tower. They will reach their full height by summer.

Those behind the project said the final cost – which was cut from an estimated £1.6 billion to £1.4bn last year – could be slashed even further due to low inflation and a lack of disputes and other delays, with the potential for the bridge to open before the expected date of December 2016.

Infrastructure secretary Keith Brown visited the Queensferry Crossing’s north tower yesterday to view the latest progress and praised the expertise and hard work of those building one of the most significant bridge projects underway in the world.

He said: “I feel lucky to get such a close look at the tower and deck construction and it’s here that the true size of this structure and the sheer scale of the operation underway to construct the Queensferry Crossing hit home.

“There are now over 1,000 people working on the project in what is a 24 hour operation out on the water. Visiting in the middle of winter reminds us only too well of the harsh and challenging conditions those building the bridge will continue to face before the bridge opens in late 2016.

“The entire scheme has been widely praised as a shining example of good, efficient project management and I am very pleased to report the three main towers now stand over 105 metres - meaning they are over half way to their final height of 210 metres. Not only that, but 10 per cent of the total bridge deck is now in place either side of the towers.

“At the heart of this Government’s Economic Strategy is the importance of boosting competiveness. Well targeted investment in infrastructure is one of the drivers of growth, and can also help to open up economic opportunities for communities and businesses. The Queensferry Crossing is an excellent example of how Government investment is helping to strengthen the wider Scottish economy.

“It’s not just out in the Forth where excellent progress is being made. Work is now underway to construct the north approach viaduct, where the final bridge will land on the Fife side. Assembly of the southern viaduct deck was completed last year and it will be launched into its final position later this year.

“Constructing and upgrading the connecting roads are a huge job in their own right. In fact there are 11 road bridges being built as part of the new approach road and junction on the south side and the significantly upgraded Ferrytoll junction to the north.

“With all of this work underway on a number of fronts I am very pleased to say that the project continues on schedule and under budget.”