David Cameron was shown the busiest section of railway in Wales, near Cardiff Central station, where the electrification of the Great Western main line and the Valleys lines will intersect.
The Prime Minister was shown round by Mark Langman of Network Rail Wales.
Prime Minister David Cameron, who's visiting the Royal Welsh Show at Llanelwedd, has announced plans for the UK Government to buy locally sourced seasonal food whenever possible. The Welsh Government already has a similar scheme.
In England, it's estimated that the public sector spends £1.2 billion a year on food, half of which is imported. The Prime Minister expects that most of the imported food could be replaced by British produce, much of it locally sourced.
No-one does more or works as hard in Wales and the rest of Britain today than our farmers. By opening up these contracts, we can help them create more jobs, invest in their businesses and make sure people in Wales have a healthier lifestyle. It’s a triple win –and will mean a brighter future for our country.
The Prime Minister refused to apologise for saying Offa's Dyke has become 'the line between life and death'.Read the full story ›
Trade unions representing around 400,000 workers across Wales have today condemned political attacks aimed at the Welsh NHS and called on the Prime Minister to apologise for describing Offa's Dyke as a 'line between life and death'.
In a public statement, marking the 66th anniversary of the NHS, unions are warning that political attacks have already damaged morale within the service and risk 'driving a wedge between patients and staff.'
Wales TUC unions within the health service represent thousands of NHS Wales workers ranging from nurses, paramedics and consultants to porters and physiotherapists.
Wales TUC General Secretary Martin Mansfield said:
"Today we should feel proud that the NHS was made in Wales, proud of the advances made and doubly proud of our committed and talented health workforce. We know that, despite political attacks from UK politicians, NHS workers have the support of the Welsh public.
"Of course there are challenges and resources are stretched, but our members see the reality of an excellent service striving to be even better in the wards, surgeries and clinics right across Wales. It is time that their voice is heard."
A Downing St spokesman said:
“The PM has set out his view on how the NHS is run in Wales and he stands by that.”
David Cameron has said that the Andrews Report into care failings at two Welsh hospitals is concerning and needs to be studied. During his weekly question session in the House of Commons, the Prime Minister said 'the NHS in Wales is not in a good state.'
It's the latest in a series of regular attacks on Labour's running of the health service in Wales made by the Conservative leader. He told MPs that Labour should be 'getting a grip... and sorting out the NHS.'
200 jobs are being created at financial research firm Avox in Wrexham by the end of 2016.
That economic boost comes after a worrying few weeks of jobs news around Wales, with 149 jobs lost at Creative Foods in Flint, 400 under threat at the Murco oil refinery in Milford Haven, 650 going at Avana Bakeries in Newport, and a further 150 under threat at the Freeman events company in Cwmcarn.
The Prime Minister was also in North Wales - visiting a furniture business in Flintshire.
The Prime MInister has welcomed the publication of the Silk Commission's second report. David Cameron said:
I am proud of this Government's record in delivering for Wales and bringing further devolution. The tax and borrowing powers we are devolving will give the Welsh Assembly and Welsh Government additional means to help generate economic growth and today's report makes recommendations that propose a new course for the future.
I know that the Secretary of State for Wales, and colleagues from across Government, will give careful thought to each of the recommendations made.
In his St David's Day message, Prime Minister David Cameron says he is looking forward to the many opportunities Wales will have this year to present the 'very best' of the country to a global audience.
St David's Day is a time to celebrate Wales' rich and illustrious history, its beautiful language and its cultural heritage. Yet this year, we also look forward to a time where Wales will have the opportunity to showcase its credentials on a truly international stage.
In September, the NATO Summit will be hosted in south Wales, providing everyone - from business leaders to school children - with a unique opportunity to present the very best of Wales to a global audience.
I hope that everyone seizes this opportunity to show Wales as a great place to live, to visit and to do business in. I'm pleased to be flying the Welsh flag over Downing Street today and I wish everyone a very happy St David's Day - Dydd Gwyl Dewi Hapus i bawb.
The Welsh flag will be flown above 10 Downing Street in Westminster today to mark St David's Day.
The Welsh flag will be flown outside 10 Downing Street today to mark St David's Day. Prime Minister David Cameron says today should be a celebration of Wales' language and heritage and that there will be many opportunities this year to present the 'very best' of the country to a global audience.
Our Political Editor Adrian Masters is in Pembrokeshire with the Prime Minister.
David Cameron has been seeing the damage done by flooding in Newgale, and visiting businesses in St Davids.
PM is in West Wales & South West England today visiting people affected by the recent flooding & local businesses
David Cameron has been visiting Pembrokeshire to see the damage done by flooding in Newgale and to meet businesses in St. David’s.
He tweeted his support for councils giving council tax rebates to residents whose homes have been flooded.
I can confirm we will fund councils that give council tax rebates to people whose homes have been flooded.