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In the five decades since its foundation Flint & Neill has amassed an enviable portfolio of bridge design and analysis commissions.Antony Oliver talks to the joint directors.

In the cut-throat, growth demanding culture of 21st century business, there is something quite refreshing about Flint & Neill's strategy.

"It's all about the engineering," explains joint managing partner Ian Firth. "We don't see any advantages in growth per se. We would grow only if the jobs require it. If we make money then great – but we are really interested in the projects."

Without question this philosophy, based around a clear passion for engineering, has been at the heart of the firm's continued success since Tony Flint and Tony Neill left Imperial College to set the partnership up in October 1958.

And their success is borne out by a quick glance through the projects now on the firm's slate – headed in no small part by the recent commission to design a new cable stayed Forth crossing.

Although working as part of a consortium involving Arup, Jacobs and Danish architect Dissing & Weitling, the project is a major feather in the firm's cap and will inevitably see the 45 strong workforce grow.

But on a personal level, the Forth Bridge design must also represent some kind of justice to Firth who had to sit by and watch Hong Kong's Stonecutters Bridge – his last major cable stay design competition – progress without him.

He describes his Stonecutters experience as something of "a sore wound" having first won the client's design competition – this time working with Halcrow – but then saw detailed design snatched away from him after the second stage bidding.

The project is also close to the heart of David McKenzie, the other joint managing partner, not least because of the way it put the practice on the world stage

Stonecutters, explains McKenzie, demonstrated that the firm could "compete with all the big boys" and work with them. "Our share of the projects may be slimmer but it's the bit that we want to do," he points out.

It is this ability to work effectively alongside much larger partners, bringing specialist structural expertise, that has given Flint and Neill its niche over the years.

And for the major part of the firm's early life, this expertise was rooted in academic structural research and specialised building work such as the acclaimed shell structures of the Baha'i Temple, New Delhi, India and Geoffrey Chaucer School, London.

The first real venture into bridges came in the early 1970s after the Westgate and Milford Haven box girder collapses. Tony Flint was on the committee of BS153 and his research interest had always been in the stability of steel plate structures. He was consequently a natural choice to become involved in investigations that led to the seminal Merrison report.

So-called "forensic investigation" became the core of Flint & Neill's work. The firm led investigations into many structural problems including the guyed mast collapse on Emley Moor in 1969. McKenzie is currently chairman of the Wind Engineering Society and a leading specialist in tall mast design and assessment.

"David and I cut our teeth on investigative assessment," explains Firth.

"I was doing that long before I did any design work. We have managed to maintain that legacy but have also built on it."

Firth and McKenzie cut their teeth at the firm on the complex and intricate Severn Bridge strengthening project – a job requiring practical problem solving, technical expertise and first principles analysis.

Today, both travel the globe to projects such as San Francisco's new Bay Bridge, China's Taizhou suspension bridge or Istanbul's Bosporus Bridge to provide clients with specialist advice and structural reassurance.

Firth says the firm's academic, analytical approach goes back to Dr Tony Flint and still characterises its ethos.

"When something has to be done that falls outside the code that's when the phone rings," said Firth. He highlights the firm's quiet involvement in the recent work to solve the Millennium Footbridge wobbles as an example.

"Arup chairman Bob Emerson made the call," explains Flint. "He knew we could add something and help solve the problem."

But it is not, he insists, just about solving problems after disaster strikes. On the contrary, checking designs before construction starts is even more important.

"Checking is a very sensible thing to do," says Firth. "It costs so little to do a design check so the question is why not? We are all human and if the designer has missed something the checker will find it."

He reflects on the clear recommendations by Merrison back in the 1970s, that design and erection procedures had to be checked. But he warns: "I fear that the lessons learnt are now being diluted by commercial pressures. Incidents like I-35W [bridge collapse in Minneapolis last year] are a wake up call."

So while checking and analysis remain at the heart of the firm, bridge design is increasingly driving its reputation. But this only really kicked off when Firth joined in 1990 and persuaded his fellow partners to let him enter the Poole Harbour crossing competition.

"None of us really expected to win the competition," says Firth. "We went into it from a desire to learn how to do design competitions. We ended up winning the job and from then on went from strength to strength on the design side."

Since then, the firm has entered and won many bridge competitions including one of Firth's personal favourites, the Bridge of Aspiration, designed with architect Wilkinson Eyre, between the Royal Ballet School and the Royal Opera House in London's Covent Garden.

Yet despite his competition success, Firth remains outspokenly critical of Royal Institute of British Architects' (RIBA) bridge design competitions which he says too often deliver poorly engineered or unbuildable designs.

"I have real issues with the RIBA and they know it," says Firth. "With a big bridge project the engineer has to take the lead. I love to work with architects but unless the engineer is strong enough to stand up to them you can come unstuck."

He is, however, looking forward to working with Dissing & Weitling – and with Arup and Jacobs for that matter – on the Forth bridge. Firth and McKenzie are already getting their heads around the implications of such a large project for the firm in term of expansion.

With big projects come big risks and for a firm of Flint & Neill's size this can be daunting since professional indemnity insurance can only go so far.

"The company has evolved around our understanding of the engineering," says McKenzie. "We manage the risk by understanding the engineering. It's what we do."

Flint & Neill: A History 50 years of engineering

Flint & Neill has been involved in a wide range of projects since it was established in 1958. Its work includes forensic investigation of failures as well as winning design competition entries and checks on high profile structures.

  • 1958
    Dr Tony Flint and Tony Neill established the firm

  • 1967-2007
    Royal National Theatre, London

  • Early-1970s
    Reconstruction of Milford Haven and West Gate Bridges

  • 1976-2008
    Erskine Bridge, Scotland

  • 1977
    Brian Smith becomes a Partner

  • 1980
    Tony Neill retires

  • 1985-91
    Severn Crossing strengthening

  • 1981-1997
    Tsing Ma Bridge, HK

  • 1981-1986
    Baha'i Temple, New Delhi, India

  • 1990
    John Evans & Ian Firth become Partners

  • 1993-1997
    Ting Kau Bridge & Viaducts, Hong Kong

  • 1993
    Tony Flint retires.

  • 1996
    David MacKenzie becomes a Partner

  • 1997
    Poole Harbour Crossing competition win, UK

  • 1997
    Brian Smith retires

  • 2000
    Stonecutters Bridge competition win, Hong Kong

  • 2001
    John Evans retires

  • 2001
    Chongming Bridge competition win, Shanghai. To be world's longest cable stay span

  • 2002-4
    Thelwall Viaduct

  • 2002
    Bridge of Aspiration, London

  • 2003
    Swansea Sail Bridge, UK.

  • 2007
    Passerelle SŹvres,
    Paris. Boomerang shaped footbridge with 80m long main span

  • 2008
    New Forth Bridge, Scotland. Part of new cable stayed crossing.

Current projects

Suspension bridges

- Taizhou Suspension Bridge, China

- Bay Bridge, California

- Severn Bridge, England

- Humber Bridge, England

- Forth Bridge, Scotland

- Clifton Suspension Bridge, Bristol

- Bosporus Bridge, Istanbul

- Fatih Sultan Mehmet Bridge, Istanbul

- Hardanger Fjord Bridge, Norway

- Lusail Bridges, Qatar

Other current bridge projects

- Compiegne Arch Bridge, France

- Port Mann Arch Bridge, Canada

- Chenab & Anjikhad Arch Bridges, India

- Third Way Arch Bridge, Taunton

- Roath Bridge Basin Bridge, Cardiff

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