Holiday resort Butlins is to sign a 125-year lease to remain in Bognor - netting millions of pounds for the town.
Its owners will sign a new lease agreement with Arun District Council on Thursday.
Under the deal, which has been formally approved by the Secretary of State for Communities and Local Government, Bourne Leisure will continue to invest in the site.
The longer lease was agreed by Arun's cabinet last October on the basis that Butlins carried out substantial investment at the resort.
The council hopes the deal will pave the way for even more money to be invested in Butlins and Bognor through schemes such as the plans for a new 200-bedroom spa hotel which could accommodate up to 720 guests, given planning permission last week.
The 200-bedroom hotel will replace the resort's former call centre building as well as 256 of its outdated apartments.
It is expected to be open by next summer.
Mrs Brown said she believed the new lease was yet another sign that Bognor was a town on the up.
She said: "We are delighted that Butlins wish to extend their stay in Bognor Regis for such a long time.
"The length of the lease indicates just how keen Butlins are to secure their position in a town that is going places.
"We are extremely happy that a name synonymous with Bognor Regis since the 1960s is joining us as we start a new chapter in the town's history, and that they are just as excited about the town's future as we are."
Norman Dingemans, Arun's cabinet member for economic and cultural development, said the deal was "yet another step forward for the regeneration of Bognor Regis".
He said: "The fact that Butlins wish to carry out such a major investment programme as well as extending their stay here for such a long time speaks volumes about their confidence in Bognor Regis.
"There is already an estimated £500 million expected to be invested in and around the town over the next decade, and Butlins' commitment to be part of this investment simply confirms the fact that businesses are keen to get involved with our regeneration plans for the area."
Butlins spokesman Richard Bates said: "Butlins has a long and successful relationship with Bognor Regis and I'm thrilled that the agreement of the new lease means it is set to continue for many more years.
"The development scheme for the Resort is really exciting and we're delighted to have been granted planning approval for our new spa hotel which will look breathtaking."
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