First it was the Corporation of London and its claim that Liverpool Street Station would be swamped by Crossrail's passengers. Then it was Camden Borough Council and its challenge on the cost of eliminating ground borne noise.
Both have left Crossrail's eminent band of barristers sounding flummoxed before the select committee of MPs currently examining the project's enabling bill (NCE news last week).
If built, the £10bn Crossrail project will provide a direct rail link between Kent, Essex and Berkshire via a rail tunnel between Paddington and London's east end. First the project needs enabling legislation before work can start, and this means exposing the plans before a House of Commons select committee.
Crossrail promoter Cross London Rail Links (CLRL) remains philosophical about the recent maulings before the committee. It points out that this is the stage of the project when objectors get to articulate their views in public.
CLRL head of public affairs Bernard Gambrill probably knows the process better than anyone, having guided the Channel Tunnel Rail Link bill through a similar committee in 1994/95. He insists there is little that can be done to pre-empt those issues which suddenly erupt into major flashpoints.
The Crossrail bill is a 'hybrid', meaning that it is treated like a private bill for part of its passage through Parliament. The process for such legislation allows individuals and bodies to oppose the bill or to seek its amendment before a select committee. And there is no limit to what they may demand.
'There are some that are a surprise. You cannot predict when the committee is going to get interested in a particular subject and you don't know on which day it's going to come up, ' says Gambrill.
'The Corporation of London had four or five days to give evidence and we just didn't know when they were going to raise Liverpool Street.' The Corporation took CLRL completely by surprise with its petition on Liverpool Street station in week one of the six month committee process. It called on CLRL to re-instate a dropped second Crossrail ticket hall that it considered essential to avoid overcrowding in what is already one of Britain's busiest railway stations (NCE 26 January).
Caught on the hop, CLRL barrister Natalie Lieven's best argument against this idea sounded unconvincing. 'If you heap too much cost on Crossrail you increase the risk of it not happening, ' she said.
And last week another CLRL barrister Reuben Taylor was forced to admit that CLRL's tracklaying costs had never been worked out in detail.
This astonished barrister Michael Clarkson who was representing the London Borough of Camden.
'After 15 years, is this the first exercise you have laid before anybody as to the detail of floating slab track?' asked Clarkson. 'Is it a finger in the wind or is it science? If it is science it is documented, surely?' The worrying thing for supporters of the £10bn scheme is that neither of these issues were identi. ed by CLRL ahead of the parliamentary scrutiny as likely flashpoints.
It was more concerned with petitions over CLRL's impact on freight paths on the Great Western Line, the siting of access shafts near Brick Lane and Park Lane in east and west London, the location of Romford depot and arrangements for the new Shenfield station.
All of these are still to come, and potentially many more besides as there are 357 petitions in all to be heard by the Commons committee before the July recess. Will these be handled any better than Liverpool Street and the noise issue?
Probably not, admits Gambrill.
Petitions are lodged well in advance, but these merely outline what their issues are - and any one petitioner may have as many as 50 concerns that it wants addressing. It is at their discretion whether they agree to talks to attempt to iron out concerns. Many prefer to keep their powder dry for their day in front of the committee 'You can't ever predict strength of evidence on any particular subject. The boxes of petitions fill an entire wall of the office, ' says Gambrill. It is only when they give evidence that their specific concerns emerge.
'They have had our material to digest for four weeks.
We usually see theirs on the morning they give it, ' says Gambrill. 'This makes it very difficult [to respond].
'We have to be quite quick on our feet in defending our position but because we cannot pre-empt the petitioners we are caught on the hop more often than not. You have got to take it on the chin.'
Once the issue has emerged it is CLRL's barristers' job to keep witnesses talking while supporting information is dug out back its Westminster headquarters and raced over to the House of Commons.
'We listen all the time to the live feed and if starts heating up can say 'For god's sake get down there!'' There is one ray of light for the Crossrail team - last week the committee chairman introduced a new rule calling for all materials that are to be presented to be exchanged the night before.
But whether petitioners will actually do this or not, we will have to wait and see, ' says Gambrill.
After being on the receiving end of a battering for the best part of a month, Gambrill remains in high spirits - he has been here before, after all.
'Like CTRL, hybrid bills normally do get built. The fact that it is a hybrid bill means it is government policy and once powers are in place (which last 10 years), it usually gets built.' This is an important distinction when it comes to the battle of the QCs being waged in front of the committee.
'We do not have to promote it, because the principle is accepted by the hybrid bill, ' says Gambrill. 'So we only defend it.
And this defence comes in the form of intense legal debate.
'They try to say our engineering judgement is incorrect. Case law is paraded out. It is not like a select committee where you get a spanking from the MPs. It is all very legal, rather like doing things before a jury with the committee chairman as judge or magistrate.' This in itself raises concerns that the complex engineering issues are being fully understood. 'Each member of the committee has different expertise. But it is doubtful if they understand the details of ground borne noise, for example, ' says Gambrill.
This, experience tells him, will be redressed when the bill moves to the Lords.
'We found with CTRL that when you get into the Lords you find engineers, scientists, bankers and lawyers who are extremely knowledgeable about the formulation of laws relating to large infrastructure.
'But even in the Commons committee they do ask questions and if they are not clear on something can have it explained again.' After the bill has been through the Commons committee a special report will be producing setting out what the promoter and petitioners must do to satisfy parliamentary undertakings. It then moves to the Lords for a similar process.
Thankfully, this is expected to be quicker. The bill will then be 'read the third time'. When both the Commons and Lords have agreed on a final wording, the bill will receive Royal Assent and become an Act.
CTRL took one week less than two years, all told.
CLRL is hoping for a similar result here.