Volunteers from Kent have been taking part in the world's largest trial for a revolutionary new test to detect cancer.

More than 100 patients a day, aged between 50 and 77, have been giving blood in a supermarket car park in Sittingbourne from 8am to 8pm – and among them was our reporter John Nurden. Here's how he got on.

A specially-built trailer for the NHS-Galleri project was stationed at Morrisons in Mill Way until last week and is now in Ashford until the end of June when the trial ends.

In all, 140,000 people will be tested. Among them was me.

It began with an invitation letter which arrived totally out of the blue and came in a large white envelope.

It announced: "We are inviting you to take part in an important research study on a new test called Galleri that may be able to detect cancer early."

How can you refuse a request like that?

All volunteers in the target age range were asked to log onto a website with a special invitation code and fill in details to register.

The letter also included a 12-page participant information sheet setting out everything about the study, what will happen to the blood samples and how our details would be stored.

There was a series of dates available to choose. I picked 10am on Thursday, May 19.

The letter confirming this warned: "We ask that you wear a face covering. Please do not arrive early for your appointment to allow us to maintain social distancing."

I'd taken a day off work for this and so, completely against my normal mode, turned up a full 15 minutes early. I was forced to twiddle my fingers in the car.

At first I didn't recognise the unit. I had been expecting to find a hastily converted van by the supermarket entrance. In fact, it was some kind of space-age complex with posh smoked-glass windows preventing the curious from peering inside.

It also had a fairly permanent metal ramp for easy wheelchair access.

At 9.55am I couldn't wait any longer so I strapped on a mask and tentatively strolled up the gangway, following the arrow.

Inside, I was greeted by a welcoming party of smiling nurses. Well, I presumed they were smiling. Like all NHS operations, they were still in Covid-lockdown mode and wearing masks. I also had to clean my hands with sanitiser.

Then I was taken to one of many cubicles where I had my details checked, filled in a two-page consent form and made to watch a video explaining what the test was all about.

It is designed to detect difficult to identify diseases early such as head and neck, bowel, lung, pancreatic and throat cancers.

It can pick up a signal for more than 50 types by finding chemical changes in fragments of genetic code which leak from tumours into the bloodstream.

Participants, who must not have been diagnosed with cancer in the previous three years, give 10ml of blood and will be invited back after one and two years to give further samples.

Only half of the samples will be tested. The other half will be used as a control group. No one will be told of the results unless cancer is detected.

"What arm do you want?" asked the nurse who had been on duty since 8am. It turned out she came from Bromley and had signed up for the entire run.

I gave up my left, believing that if anything "happened" I would still have the other to write with.

I've had blood tests before but this one did seem to involve giving a larger than usual vampire-like amount.

However, it didn't hurt and after completing an online survey I was soon outside clutching my free £10 Morrisons voucher. Every volunteer was given one to spend in the store.

Inside the supermarket I discovered that nearly every other shopper must have been giving blood, too, as they were lining up to buy goods with their own vouchers.

We all spent way over a tenner. What a brilliant piece of marketing that is!

The project has been running across eight areas of the UK, including Kent and Medway, since September last year.

Kent and Medway cancer alliance programme director Ian Vousden said: "The response has been fantastic from patients. The mobile unit has been across Kent for just over six months. Sittingbourne and Ashford are the last two."

He added: "We’re looking forward to seeing the overall results of the trial next year.

"We know patient outcomes are so much better when cancer is detected early. But some are hard to spot. This trial has the potential to change that. If successful, this test could be used in routing screening.”

The trial is being run by Cancer Research UK and King’s College London Cancer Prevention Trials Unit in partnership with the NHS and American healthcare company GRAIL which has developed the Galleri test.