IS it a bird? Is it a plane? Or is this UFO an alien craft which has picked up episodes of Hollyoaks and come to visit the real-life inhabitants?

Whatever the origins of the visual phenomenon, it was spotted in the skies above Blacon by Steve Culshaw and his partner Erika about 11pm on Sunday.

Both describe it as a black triangle with white lights in each corner and a red light in the middle, which was just a few hundred feet up. The noise was like a loud drone unlike any normal aircraft sound.

The craft, which was said to look bigger than an airliner, came from the Runcorn direction, hovered over Blacon, and then darted off towards Queensferry.

UFO experts say it bears a striking similarity to other sightings across the North West. They speculate it is an experimental military aircraft which is being kept under wraps.

Steve, who lives in Fowler Road, Blacon, said: 'My girlfriend was in the kitchen. We were just going to go to bed and then she said 'Look at that huge star in the sky'. It was way, way, in the distance. We were looking over towards Runcorn. It was sat there for ages.

'I said 'I don't think that's a star.' It was too bright. The light was nearly touching the ground. Then it started to move and got closer and closer.

'I went outside into the back garden and it was 300ft above my head. I thought 'Oh my God'. I could see lots of lights. It went between the high rise blocks. It was a triangle shape with three lights - one in each corner - and a red one in the middle. It was making a humming noise. It went round the front of the house and then towards Queensferry.'

Mr Culshaw is under the flight path for Hawarden airfield, which was closed at the time, and sees lots of aircraft but does not believe this was a plane.

'No way. The shape was totally different. I see lots of planes coming over with lights. This was totally different,' said Mr Culshaw, although he admits at the time the thought crossed his mind it could be a US Airforce Stealth aircraft.

Mr Culshaw, a volunteer at the Well Blacon holistic therapy centre, said he was not frightened but 'fascinated' by what he saw.

'I was in the Army 24 years,' said Steve. 'I'm pretty grounded and I'm used to observing things. As it moved away it reminded me of a Stealth but it was moving too slowly, unless they've got new technology which can make it hover.'

'The closest thing I can relate the noise to was in the Army. With radar we had silent generators to keep the noise down. It sounded a bit like that.'

His partner Erika Tetley said: 'I thought it was a star at first but it was massive and really low down.

'I said "Come and look at this star, it's massive". Then it moved very, very, slowly, next it started to speed up. It was really low and going over our heads.

'I don't think it was an aeroplane. I've seen plenty of planes going to Aerospace but the shape was different, like a triangle, but the ends were not pointed but rounded.'

She said the pair of them must have watched the craft, which made a 'loud hum', for about 10 minutes in total.

UFO investigator Dave Sadler, an aircraft engineer at British Aerospace at Broughton who is also a leading member of the Para.Science organisation, believes the 'triangle' sighting was of a prototype military aircraft.

He said: 'It's not unusual in this area. I'm involved with UFO studies and within the North West, from Preston down to Manchester, there have been sightings, particularly in 1999 and 2000. I believe it's an experimental aircraft.'

Mr Sadler, who lives in Ellesmere Port, added: 'A similar issue came up with the Eurofighter. Back in the 90s nobody knew what it was.'

About six months ago he received reports of another triangular object, but without lights, which was spotted at Tarporley. He said the most recent report of a UFO prior to this was an unusual light over Pensby, Wirral, last Thursday.

An air traffic controller at Hawarden Airport dismissed the possibility the UFO was anything to do with them, explaining that the airfield had been closed from 4pm that day. He suggested: 'It could have been an optical illusion. You can get them at night. It could be an aircraft's headlights or something.'

A spokesman for the Civil Aviation Authority, which regulates civilian flights, passed the enquiry onto his military colleagues.

He said: 'I'm only speculating but it sounds like an F117 Stealth fighter.' He said talk of experimental aircraft was 'fanciful'.

Ministry of Defence spokeswoman Caroline Edie said: 'I don't doubt what is being said. But at

23.00 on Sunday night I can be almost 99% positive it would not be a military aircraft.'

A US Airforce spokeswoman said: 'I checked with both bases and no-one was doing any night flying on Sunday at 23.00 on 29th February, so you can rule out the United States Air-force.'