Hammerson's offer of 253.9p per share represents a 28% premium to Intu's closing price on Tuesday but a 34% discount to the last reported European Public Real Estate index net asset value.
Mr Atkins described the United Kingdom retail market as "challenging" and said that there is a "polarisation" between the best and worst shopping centres.
Russ Mould, AJ Bell investment director, described Hammerson's takeover of Intu as "dramatic, given how terribly Intu's shares have down this year, amid fears over not just what Brexit may do to consumer confidence but also the fate of bricks-and-mortar retailers at the hands of Amazon and other online rivals".
The combined group will be led by Hammerson boss David Atkins and chaired by David Tyler.
It expects pretax benefits for the combined company to reach a run-rate of about 25 million pounds per annum by the end of the second year.
Shareholders will vote on the deal next year, with Intu having already secured more than 50% of investor support for the all-paper deal. "The financial strength of the Enlarged Group and its strong leadership team will make it well-placed to take advantage of higher growth opportunities on a pan-European scale".
Intu’s share price is on the rise
It will combine Intu, the owner of Manchester's Trafford Centre, with the FTSE 100 company behind Bicester Village in Oxfordshire, London's Brent Cross shopping center and Bristol's Cabot Circus to form a group that will also have sites in Ireland, France and Spain.
Markets cheered the news, with Intu's share price jumping 22% to R44.19 in early trade on the JSE.
As of 09:54 GMT, Hammerson's share price had given up 2.06 percent to 523.50p, underperforming the broader United Kingdom market, with the benchmark FTSE 100 index now standing 0.14 percent lower at 7,317.20 points. The group overall will have six directors nominated by Hammerson and four directors nominated by Intu.
However, shopping centres in city locations have tended to fare better than high streets during economic downturns.
Hammerson shareholders will own about 55 percent of the new company and Intu investors will own the rest.
Atkins added: "This marks an exciting milestone in the history of Hammerson".