Property experts claim the shorter travel times when the tracks are fully electrified will mean more London commuters move further out of the packed capital city - including into homes in Bristol.
An annual season ticket from Bristol to London is currently £10,732, but in many cases, that still makes life cheaper than trying to buy a property in London.
The relocating workers and new demand is likely to inflate property prices up everywhere from Weston-super-Mare to Bath, according to experts.
James Toogood, the head of Bristol estate agents Knight Frank, said: “This potential growth has not yet been realised by those outside the property industry.
“But it will become more apparent as 2017 approaches.
“The shorter journey time will definitely push prices upwards. I’m expecting house values in Bristol to rise somewhere between five and 10 per cent above the standard market increase.
“In the past, most of our London buyers have been people moving to Bristol full-time. Now, though, I think we will see more buyers wanting to work from the Bristol office two or three days a week. On the other two, they will commute to London.
“We have many big employers here, such as law firms Burges Salmon and Osborne Clarke, plus a good number of large accountancy and technology firms.
“We have a home in Cotham for £625,000. A similar house in London’s Earlsfield or Balham would cost a million pounds. The average price per square foot in the prime Bristol area is £309, as against £450 in prime Home Counties areas.”
The new electric trains - which will slash the current journey time to the capital of 1hr 40m by 22 minutes - will use 21 per cent less carbon and they will also inflict 13 per cent less wear and tear on the track.
Work to install the line is happening at night, and is currently creeping towards Bristol at a rate of one mile a night. It will reach Oxford, Newbury, Swindon and eventually Bristol and South Wales at the end of 2016.
It’s not just around Bath and Bristol that the faster trains are being welcomed.
Knight Frank estimates the areas that will benefit from the faster trains include a huge area that stretches from Monmouth in the north to Shepton Mallet in the south, and from Weston-super-Mare in the west to Chippenham in the east.
Their calculation assumes that commuters would be willing to drive for up to 40 minutes to get to the station.
Richard Brookes, the head of residential at Savills, in Bristol, said: “A lot of would-be commuters might write off the idea of a one hour and 45 minute commute. Psychologically, that 22-minute saving could make all the difference.”
In 2012 the Government signed a £4.5 billion pound deal with a consortium led by Hitachi to build the new inter city trains which will serve the Great Western route.
The new fleet is being built in the North East but as part of the deal the consortium has built the new maintenance depot in Stoke Gifford, which created around 200 jobs in the area.
Temple Meads station will also be modernised and two new platforms created along with a new entrance.
The trains will have more seats and generally more space than existing high-speed trains and will accelerate faster than existing rolling stock.