After establishing two of East Anglia's foremost nature reserves Norman Sills has just retired from the RSPB. He spoke to KEIRON PIM.

Midway through comparing nature conservation today with when he entered the field almost half a century ago, Norman Sills interrupted himself: 'Look, there's a marsh harrier. From the way it's flying straight and fast I'd say it's caught some prey and is heading straight for the nest – there's one down there,' and with this he gestured to a spot in the thick of a reedbed, a hundred yards or so away.

The hawk veered left and descended toward the reeds, revealing on the turn a pair of talons clutching some unfortunate small mammal; then it was gone. 'The youngsters will be big enough to rip it apart themselves by now,' he said. Nothing else stirred for a few moments and anyone who did not know better might think the landscape deserted rather than rich with hidden birdlife.

It is quite something to have complete comprehension of an environment but an hour in Norman's company at Lakenheath Fen suggests that he knows every square foot of this wetland habitat west of Thetford. It shouldn't be a surprise, however, as he almost singlehandedly created it – or rather, oversaw the restoration to its natural condition after more than three centuries spent drained of water and scoured of its wildlife. Think of fenland and you picture the desolate flat expanses of east Cambridgeshire but once, before the Dutch engineers helped clear the water and create black-soiled fields, this was what fenland meant: a wild, marshy environment comprising reedbeds and meandering waterways.

'Going back 400 years there was 1,500 square miles of what you have in front of you,' said Norman, sitting on a bench in a shelter by Joist Fen, one of the reserve's two reed-banked expanses of water.

'Mankind was there of course, with grazing cows, but it wasn't drained. You had a bit of piecemeal labour by the inhabitants, with thatching making use of the reed. But once we had invented steam power and electric power, we could drain the whole area. It's good to see that mankind also has the ability to put it back to how it was.'

The story of Lakenheath Fen's revival began in 1995 – with typical precision Norman recalls the first sod being laid on October 31 of that year. Then came nine years of hard work: fields excavated and inundated, reedbeds cultivated, an old 17th century drainage channel diverted and enclosed. Between 1996 and 2000, he and his team of volunteers planted more than 300,000 reeds along the water edges. The waterways and 24 sluices were developed with the help of a hydrologist named Prof Gordon Spoor, whose expertise ensured that they created just the right balance to support wildlife. There are now more than 60 hectares of reeds and 25 hectares of water.

Norman has just turned 65 and retired from his role as site manager, having spent the last 40 years establishing this and another of our region's prime nature reserves: first came Titchwell on the north-west Norfolk coast. He grew up in Coventry and retains a hint of a West Midlands accent, and began what later became a career by volunteering as a teenager at a Warwickshire nature reserve.

'In Sir Peter Scott's autobiography, I think his opening line was 'I consider myself to be the luckiest man I know'. I can identify with that. My father said I would never make a career out of birdwatching. In the late 1960s it wasn't on the cards – very few people went into conservation.'

Then in December 1970 he saw a recruitment advert for two RSPB wardens at a site in Teeside. He got the job and spent the early 1970s there, and then 'went on holiday to the north Norfolk coast and my mate introduced me to a little village called Titchwell. We walked along and I saw the potential for a nature reserve: reedbeds, shingle beach, saltmarsh… I wrote to my then boss, said I have found this place and had he heard of it?, and he wrote back by return of post and said 'We have just bought it, and would you like to be the warden?'. So I moved there in 1973 and had 24 years there.'

After that the work at Lakenheath began in earnest. The plan was to create an environment to suit bitterns, which had become emblematic of Britain's threatened birdlife. The plan succeeded, and some. Single bitterns were recorded on two dates in 2002 and 2003, then on 15 occasions in 2005... and by last year there were five bittern nests. Then came what he calls 'the cherry on the cream on the cake'.

'When the fens were the proper fens, cranes nested there, but they didn't adapt to the new drained landscape and for the last 400 years there hasn't been anywhere in the fens where they could come and nest. Lo and behold in 2007 two pairs rolled up and the same two pairs are here today. You can get these nice surprises and it's part of the magic of this place.'

RSPB Lakenheath Fen is open daily. Parking is free for RSPB members and �2 for non-members. For more information telephone 01842 863400 or email lakenheath@rspb.org.uk