But whereas previous projects have won the 65-year-old plaudits and a knighthood, this one has attracted unprecedented criticism. The press and public have pilloried its appearance, with architecture critics calling it "as leaden as it is charmless" and "black and forbidding … a Transylvanian fortress".
MPs have complained of teething troubles since moving in last summer, including fire alarms and sprinklers going off without warning, a lack of storage space and few places to plug in kettles.
"I could not have justified its expenditure," chancellor Gordon Brown said last month, adding his voice to the chorus that has attacked its exorbitant cost.
Hopkins has kept his head beneath the parapet of late and has declined to be interviewed by Building. Whether this was because of the storm surrounding Portcullis House is hard to tell: he has always kept a relatively low profile. Arguably the third most esteemed living architect after Lords Foster and Rogers, he has nothing like their public profile and is regarded as something of an elusive figure. "He wants the architecture to speak for itself," explains a colleague. "He is very much a doer rather than a talker," says another.
The signs are that he is wise to let the dust settle on Portcullis House. Already a growing body of opinion predicts that once the furore over the cost has died down, people will start to appreciate the building as an exemplar of environment-conscious design, and an object lesson in structural integrity.
"I think Portcullis House will be a slow burner. It does not meet with immediate universal approval, but it stands up to closer examination. It has a structural logic, consistency, clarity of detailing," says a colleague of Hopkins.
"You may not like how it looks, but it is a very tight piece of design. Every part of the external envelope has functional criteria derived from environmental logic," says a project source.
Although MPs continue to wring their hands over accusations that they have been profligate with public money, Hopkins has been largely exonerated from blame for the cost overruns, which have been attributed to bungled procurement, unforeseen construction contingencies and inflation. It seems he will walk away from the project with his reputation intact, as well as fees calculated as a percentage of the inflated construction cost.
Hopkins has a reputation for designs that are expensive and hard to build, and that often result in contractual wrangling. He will not be on the Christmas card list of many trade contractors, one of whom says he is "notoriously difficult to work with on a day-to day-basis, to get approvals to build and get things done".
Hopkins' clients have also been on the receiving end of the same stern treatment. "He achieves buildings of great integrity by being tough with clients. He will not let a commercial client water down or weaken his ideas," says a long-standing collaborator.
And former staff of his 100-strong Marylebone office say he "does not suffer fools gladly" and is extremely exacting. "He is a master at being difficult and asking the awkward question," says one former colleague.
Yet his supporters argue that it is only by being so tough that he is able to execute his designs, and that Portcullis House is a tribute to his determination and conviction. "He is good strategically; he can hold his nerve and see his way through the morass of relationships, publicity and different agendas on projects," says a colleague.
He is a master at being difficult and asking the awkward question
Lord St John of Fawsley, who commissioned Hopkins to design the Queen's Building when he was master of Emmanuel College Cambridge, seconds this. "We had some terrible times with the fellows at Emmanuel, but Michael always won them over with a combination of firmness, tact and sheer knowledge." Hopkins' wife and partner Lady Patty Hopkins, who jointly won the Royal Gold Medal for Architecture with him in 1994, is reported to be a powerful asset in this regard. "They are working from Michael's philosophy, but she is a strong support. When they make presentations together, she is delightful, very articulate and very knowledgeable," says urban design consultant Richard Coleman.
And despite his reputation for being difficult, Hopkins continues to attract the most elite clients in the land. As well as the Marylebone Cricket Club and Glyndebourne opera house, universities, arts bodies, government departments and local authorities have lined up to commission his buildings. Live projects include the £25m extension to Manchester City Art Gallery, a leisure complex at Hampshire County Cricket Club, a £4m redevelopment of Goodwood racecourse, and a £60m library complex in Norwich, known as the Norfolk and Norwich Millennium project.
Some trace Hopkins' charmed career back to 1988, when Prince Charles commended the Mound Stand at Lord's as a shining symbiosis of modern and traditional architecture. Hopkins was then embraced by the establishment as the acceptable face of modernism and has never had to look abroad for work. Even the barrage of criticism over Portcullis House is unlikely to dent the support of heavyweight patrons and friends, including former arts minister St John of Fawsley, the former chairman of the Arts Council Lord Palumbo, and former English Heritage chairman Sir Jocelyn Stevens. "He is very powerful. He knows everyone," says one of the many former colleagues who will not go on the record to talk about him.
So what is the Hopkins product that these elite clients all want? "He has a peculiarly English sensibility as regards care and attention and his desire to put things together in a well engineered sense," says a former colleague. If a building by Zaha Hadid or Daniel Libeskind is an Issey Miyake couture creation, a building by Hopkins, would be an impeccably tailored Savile Row suit.
He has been less prolific than Rogers or Foster, with whom he worked at Foster Associates until 1977, and some see this as a strength. "Richard and Norman have done enormous quantities of work. Michael very carefully picks projects that allow him to pursue his philosophy of architecture," says Coleman.
St John says his strength is his ability to bridge the gap between tradition and modernism. "He combines a modern approach with classical form and proportion, so you get the best of all worlds. Also, his use of materials is extraordinary. He doesn't economise and he doesn't compromise." "The way he puts buildings together and the way they are constructed is very legible and clear and that is a very attractive thing. They are beautifully crafted," says Coleman.
For John Berry, a director of engineer Arup and long-term collaborator with Hopkins, his hallmarks are "integration and comprehensibility". "You can see what things are doing. He does intelligent facades always expressing structure and precast forms." Yet such "exquisite detailing" does not come cheaply or easily, as contractors who have worked with Hopkins point out. Because he designs bespoke buildings, characterised by expressive use of traditional materials, they often require untried construction methods.
Judge Humphrey Lloyd's judgment on the Harmon affair, in which Portcullis House's cladding was unfairly let to a partly British bidder, said that the "Hopkins factor" discouraged contractors from bidding.
"There has certainly been a definite cooling-off of enthusiasm for the project, driven by market, uniqueness of design, uniqueness of material, the 'Hopkins factor' and non-standard procurement strategy," said the judge. He continued: "It was thought that Michael Hopkins and Partners and its requirements ('the Hopkins factor') would effectively make the project less attractive and thus more costly." Moreover, there are contractors who say that although Hopkins does brilliant, strong concept designs, he relies a lot on trade contractors for the detailing. What's more: "They never sign off your work," says one who has worked with Hopkins on several buildings. "They have a bible for a defects list and it is impossible to get through it all." As a result, clients and contractors are often left to troubleshoot.
The Hopkins statement counters that this is not unusual practice. "We have always developed the details of our buildings in conjunction with trade contractors and specialists," it adds.
On the £30m Jubilee Campus at Nottingham, completed last September, cladding and fit-out contractors threatened to sue Nottingham University for extra work that arose from what they say was poorly detailed design by Michael Hopkins and Partners. The practice this week says: "Virtually all of the final accounts, including the cladding, have now been settled within the authorised budgets of the university." One trade contractor says these problems with troubleshooting come about partly because Hopkins quickly delegates projects to young recruits, once they are on site. The contractor says: "It is common for big-name architects to have a flow of graduates, but Foster and Rogers have a better way of managing them, so they have a clearer understanding and better able to make decisions." A former staff member's comments seem to bear this out: "He throws young architects a lot of responsibility early on. You are in at the deep end and you either sink or swim." The practice denies that it delegates projects to inexperienced staff: "Young architects in our teams physically work alongside senior staff and mentoring is therefore part of the modus operandi." In recent years, Hopkins' reliance on inexperienced staff may have to do with the fact that many directors have left. John Pringle, Ian Sharratt, Bill Dunster and Brendan Phelan have all set up on their own or moved on. Some put this down to Hopkins' paternalistic approach to running the office and his reluctance to relinquish design control to the next generation. The practice responds that out that 10 of the practice's 14 current directors joined directly after architecture school. "We operate a 'grow your own' philosophy of bringing our architects on through the practice," it adds.
This prompts the question, who will take over at the helm when Hopkins takes his well-earned retirement – no doubt to be spent between the beach house in Norfolk and the villa in Tuscany he and his wife have been renovating for years.