The Crown Estate has acquired Rhu Marina for "an initial" £4m as part of the government property division's strategy to grow and invest in Scotland, The Herald has learned.

The acquisition was made from "a consortium of local businessmen who don't have a high profile," according to a spokeswoman for The Crown Estate.

"Further payment is linked to the development plans," she said. "The site is earmarked in the local plan for development."

The acquisition of the 6.5-acre, 175-berth site on the Firth of Clyde, near Helensburgh, includes moorings, boat storage areas, marine workshops and chandlery as well as the RNLI station with slipway and HM Coastguard.

However, a masterplan for the site, which includes an expanded marina area and related businesses, as well as upmarket apartments, is now being drawn up for The Crown Estate by Edinburgh-based architectural firm RMJM, best-known for its work on the Scottish Parliament building and the Gazprom headquarters in St Petersburg.

Alasdair Rankin, from The Crown Estate, said: "Any additional payments, and indeed the level of any future investment from The Crown Estate, will be dependent upon the nature of any development that goes ahead, and the outcome of any finalised masterplan."

It is understood that the new plans envisage that the number of berths will almost double and there are also plans for increased car parking and a new restaurant.

Rob Hastings, The Crown Estate's director of Marine Estate, said: "Rhu Marina is one of the best-known names in the marine leisure industry in Scotland and so it is fitting that this is our first purchase of a Scottish marina.

"This is an excellent opportunity for us to invest in the growing marine leisure industry in Scotland and is the first of a number of investments we hope to make as part of our new marine investment strategy."

The marina will now be leased to Quay Marinas, which also leases Deganwy Marina in North Wales from The Crown Estate.

Scotland's performance for The Crown Estate in the year to the end of March 2007 represented 5.1% of the total UK net revenue surplus, which has risen by 4.9% to £200.1m, all of which is paid to the Treasury.

The Crown Estate last year formed a joint venture with Hercules Unit Trust, combining ownership of the Fort Kinnaird retail park outside Edinburgh with its ownership of two retail parks in England.

It also recently invested £320,000 into new developments at Tobermory harbour.

The Crown Estate described the acquisition at Rhu as "a major boost to the growing marine leisure market in Scotland". The marine leisure industry makes a major contribution to Scottish tourism. It is estimated to be worth almost £3bn in the UK and is growing in Scotland at a rate of more than 10% a year.