Earlier this week anyone visiting the Oxford Castle Quarter or looking up from New Road might have been surprised to see a team of burly hunks harnessed up in climbing gear looking as if they would be more at home up a mountain.

In fact they were the boys from Oxford Garden Design, and they were there to cut the grass! We were thrilled to win the contract to clear Oxford’s Castle Mound of overgrowth and give it a proper tidy-up.

In other words, to give this ancient monument a makeover. The Mound is a heritage site, built in Norman times just after 1066. But it is several years since it had a good mow and spruce-up, now long overdue. The task wasn’t straightforward. The steep slope presented a real challenge to safety for the men doing the work and for passers-by.

We decided that the only way of getting the job done safely was to tackle it using strimmers and mountaineering gear. And, as luck would have it, my team included both an experienced mountaineer and a trained abseiler.

Aris Escalona, our project manager, is from Venezuela and spent eight years climbing in the Andes. Having reached the summit of Pico Boliva, Venezuela’s highest peak at 4,978 metres, it seemed reasonable to assume he could manage the Mound, at 18 metres. The other abseiler was Paul Norton, who learnt his technique in New Zealand.

Conquering the Andes notwithstanding, the guys went on a thorough training course before we did the work. And it was still the first time they had abseiled and cut the grass at the same time. By the time you read this the job will have been finished. All but one pesky problem.

My last column was about tackling my old foe the wasp. At the Castle we were faced with an even more deadly enemy – the dreaded Japanese knotweed.

Not unattractive, and first imported for decorative planting in the 19th century, Japanese knotweed has lush green foliage and a bamboo-like stem with white autumn flowers.

Don’t be fooled: it is a stealthy and voracious invader which can severely damage the foundations of buildings and structures, roads and other surfaces, as well as underground services like drains and sewers.

And it’s a fast mover. This weed can grow a metre in a month. Studies have shown that a 1cm section of rhizome can produce a new plant in 10 days. Plus, rhizome segments can remain dormant in soil for 20 years before producing new plants. So it’s tough to destroy.

Japanese knotweed is a controlled waste notifiable to the Environment Agency and legislated for by the Wildlife and Countryside Act 1981. The police are even authorised to investigate anyone deliberately planting it in the wild.

However, rest assured we will destroy the blighters. Castle Mound has stood for nearly 1,000 years, built to withstand the onslaught of all invaders. It won’t be beaten now!