Strikes have reached David Cameron's doorstep as the Number 10 gardeners go on their first walkout in 37 years.
Downing Street staff will walk out for 12 hours over a pay wrangle - and complain some of them aren't being paid the £9.15-an-hour London living wage.
The famous garden's maintenance contract was handed over to a private firm a year ago, and groundsmen are now angry at the company's pay plans.
It follows a planned bank holiday strike by Network Rail staff which has now reached the High Court.
And it comes shortly before the government pushes through a new crackdown on unions by making it harder to take industrial action.
All the staff are GMB union members employed by the Royal Parks, who maintain Hyde Park, St James's Park and Green Park in central London.
That means their strike will also affect the Queen, hitting the three parks around Buckingham Palace a day before she leads the State Opening of Parliament.
Royal Parks staff are also responsible for Kensington Gardens, next to William and Kate's official residence, and the Prime Minister's garden at 10 Downing Street.
In the first Royal Parks strike since 1978, they'll be protesting outside their workplaces including the PM's residence from 6am to 6pm on Tuesday - and want him to back them.
Regional organiser Gary Carter told Mirror Online: "I hope the Prime Minister now he's supporting 'working people' will support the strike. But that may be too much to ask."
The row centres around the employer, Outsourced Client Solutions, moving from weekly to monthly pay.
The union says OCS is paying two week’s pay as a 'loan' which will be 'recovered' over 12 months.
A spokesman said: "This will put staff into debt and wipe out any pay award. The two weeks' pay will only be paid when staff leave."
The GMB claims OCS won its contract a year ago by offering to run the parks for less money than competitors and is now trying to 'claw it back'.
Mr Carter said: "The taxpayer will foot the bill if they try and get money out of the Royal Parks. It'll be the same if our members are claiming extra tax credits.
"New starters are getting £35 less a week than current staff. Some people are being paid less than the London living wage. They're earning about £7 an hour."
An OCS spokesman told Mirror Online: "Over the last three months, OCS has consulted with staff and representatives of our recognised trades unions on a change to monthly pay for our staff working at The Royal Parks in London.
"This change is part of a UK payroll consolidation project moving all employees to monthly pay, which we are making for reasons of efficiency and in order to reduce the errors that result from a large volume of varying payroll runs.
"In response to staff concerns, we have staggered the changeover period in order to minimise the impact on our staff.
"We are also offering an interest free bridging loan to cover the two-week gap between the last weekly pay date and the first monthly payment.
"In response to staff requests, the repayment period for this loan has been extended from three to twelve months.
"OCS is not withholding any pay from any member of staff and there is no question of anyone suffering a loss of earnings.
"OCS is disappointed that the GMB has initiated a dispute on this occasion and we are working actively to resolve this matter via ACAS."