It is a company that claims: “You can do it if you B&Q it”.

B&Q will build a tower at Chelsea

But like the best-planned DIY projects, B&Q’s Chelsea Flower Show garden has run into a few technical difficulties.

Plans for the £300,000 vertical allotment, a tower rising 30ft (9m) high (right), have been tweaked in the run up to the May show.

The garden is to sit in front of the BBC rooftop studio where Alan Titchmarsh will host BBC coverage. Alan, who has a controversial three-year contract to promote B&Q garden centres, is not allowed to comment on the B&Q garden or report on it at the world-famous show.

AG received a tip-off that the garden was being altered so it cannot be seen on TV when Alan is presenting Chelsea coverage – a claim that’s been dismissed by B&Q.

B&Q garden designer Laurie Chetwood told AG the garden had been redesigned to sit on a triangular site, and to avoid damaging a main sewer. Laurie said: “We’ve had one hell of a problem with underground sewers. The sewers go one way, and the Underground goes the other. As designers, we have to make sure that we don’t crack anything. This has no connection with the BBC or with Alan.”

AG asked the RHS if the garden was being altered to avoid a conflict of interest with Alan’s B&Q contract. An RHS spokeswoman replied: “In the lead up to Chelsea, there are always tweaks to accommodate gardens in the most appropriate manner.

“The RHS, BBC and the garden’s sponsor always work together to ensure that BBC coverage is editorially uncompromised,” she added.