A £5m investment programme at Norfolk's oldest established beet sugar refinery has been welcomed by growers' leader David Papworth.

British Sugar's plans to invest in more storage at Cantley will send a positive signal to about 500 growers in east Norfolk and Suffolk, who deliver almost 20pc of the national crop.

'This will be a boost for growers and could help to reduce the length of the campaign,' said Mr Papworth, who is a member of the National Farmers' Union's sugar board and chairman of the beet reception for the four factories.

'Sugar beet is a cornerstone crop in our area and the factory has just not performed in recent campaigns. It is making our campaign a fortnight later than it needs to be and causing disruption to the sugar beet harvest,' he said.

He was speaking at the third of the four British Beet Research Organisation's open days at Carleton St Peter, near Loddon, which was held by permission of Matthew Hutton and partners.

British Sugar announced plans in late February to increase the capacity of 'thick juice' or part-refined sugar storage from the existing 14,800 tonnes. It will increase the height of two sugar syrup tanks and add a new storage silo, which would increase the site's total storage capacity to about 50,000 tonnes.

Mr Papworth said that the lack of thick-juice storage has sometimes been a limiting factory to the daily slice, which should be at least 9,000 tonnes each day.

'The actual slice rate has been a problem. In the 2012 campaign last year the slice was abysmal and in 2011 the limiting factor was the sugar end. Assuming a normal year, we would like to think we could get to more than 12,000 tonnes of slice in a day.'

As Cantley produces granulated sugars, in some campaigns British Sugar has slowed the daily slice because it could not process enough. All the other factories, including the world's largest beet refinery at Wissington, near Downham Market, have big juice storage capacity.

'This gives the flexibility in processing and means that more beet can be sliced,' said Mr Papworth.

'If there is a hiccup on the sugar side, it would not immediately stop everything as has happened in the past. There is not the on-site thick juice storage. It is built as an insurance if something slows the sugar end processing, so the whole factory doesn't have to grind to a halt. It is just common sense,' he added.

In 2011, which was a record sugar year and British Sugar refined more than 1.3m tonnes, the processor had to slow slice rates at all its factories because it had run out of storage, said Mr Papworth, of LF Papworth, of Lodge Farm, Felmingham, near North Walsham.

With the factory able to produce about 2,000 tonnes of part-refined sugar each day, it only had about seven days' storage. Other factories have the ability to refine out of campaign because they process stored 'thick juice'.

The plans for the Cantley factory, which marked its centenary as the first modern beet sugar refinery in 1912, include a new silo standing 28.2m high with a 50-metre diameter. The two existing tanks will be raised by 4.27m and the largest by 4.37m.

One of the largest investments in storage was made more than 15 years ago when a new tank was built, which had to be 'floated' a few metres using a hovercraft technique, on to its permanent foundations.

Mr Papworth is a member of the White Cross beet harvesting syndicate which delivers more than 100,000 tonnes of beet to the factory during each campaign. He said that the factory had been 'starved of investment' in recent years.

'From the growers' point of view, this investment is crucial and the factory needs to move forward. It is good for jobs and agriculture in Norfolk needs the investment,' he added.