...artists scoring their debut hit was back in 2004:

 

McFly - 5 Colours In Her Hair

Eamon - F**k It (I Don't Want You Back)

Frankee - F U R B (F U Right Back)

 

and the next #1 was Mario Winans, whose only previous chart appearance was as a featured artist on Puff Daddy's Best Friend.

 

To find the last instance of 4 in a row, you don't have to go back much further:

 

Michael Andrews ft Gary Jules - Mad World

Michelle - All This Time

LMC vs U2 - Take Me To The Clouds Above

Sam & Mark - With A Little Help From My Friends

This could change next week, if Morrissey, or The Streets go to No.1, it seems we could end up having a different No.1 each week, I remember one year there was a total of 42 No.1s

Thanks Paulgilb,

 

So we just had Chico, Orson and Ne*Yo

Next weeks new possibilities include Andy Abraham and Gnarls Barkley.

Could be the Streets will end the run, we'll have to wait and see.