This explanation just doesn't cut it

The Giuliani camp has come up with some sort of explanation for the billing practices that Politico exposed a couple of days ago.

-- Rudy Giuliani said yesterday that obscure city agencies were billed for the out-of-town credit-card charges of his mayoral security detail because the NYPD was so slow in paying its bills.

Hoping to limit the fallout on his presidential campaign, Giuliani told CBS's Katie Couric that the practice began during his first term and was a matter of convenience - not a sinister plot to hide expenses like time spent with then-girlfriend Judith Nathan.

"Since the Police Department would sometimes be slow in payment, City Hall would pay it first and the Police Department would reimburse every single penny of it," said Giuliani.

That just doesn't make sense. Why would the Police Department be slow in paying its bills? Why not address that problem instead of some wacky accounting procedure to have other offices pay its bills? And did the Police Department do this for all its expenses or only for those involved in Giuliani's travel expenses? Either answer would be bad. If it only did it for his travel - why? If they did it for everything, why didn't Rudy, who prides himself on his management skills, do something to clean up a practice that just was begging for some sort of planned or inadvertent use of that money?