The volume of floorspace available to be sublet from existing occupiers in London has soared by 67% since lockdown began in March, Property Week can reveal.

The amount of so-called ‘grey space’ on the market in the capital has increased from 3.02m sq ft in the middle of March to 5.03m sq ft at the start of October, according to data collated by Savills.

Mat Oakley, director, commercial research at Savills, said the volume of grey space on the market increased slowly during lockdown but then grew quickly during the summer.

“It definitely accelerated,” he said. “At the start of lockdown, there was about 3m sq ft of sublet space on the market in central London.

“By the beginning of June, it had edged up a bit but now, as of the beginning of last week, we were up to just over 5m sq ft. We’ve added 2m since the beginning of lockdown.”

Oakley added that there was no discernible pattern to which sectors were seeking to shed space and that most spaces hitting the market were relatively small.

“It’s still predominantly and comparatively small chunks,” he said. “Around three quarters of it is in units of less than 15,000 sq ft. We haven’t seen any really big corporate disposals. It’s a floor here, half a floor there – that kind of quantum.”

Oakley added that while that remained the case the amount of grey space on the market was unlikely to have an impact on rental levels in London. However, he warned, that could change.

“If it keeps going at this rate and if we see bigger corporates releasing bigger chunks of space, then you will get to a situation where you will have some high-quality sublet space that is directly competing with landlord-owned new-build space. And that’s when it will trigger falls in rents.”

News of the increase in grey space comes after Property Week reported in July that the number of ‘zombie occupiers’ – tenants with space surplus to requirement – had risen dramatically during the crisis because occupiers were rethinking their space requirements.