How long to stay in UK after HO receives application ?5 days

Hi all,
Please point to me where there is any such requirement after HO gets your application.It does say that you should be in UK on the day the application is recvd.
NCS did mention that one has to sign something to that effect? Any one know this?
Thanks

I was told by NCS staff is the applicant has to be present in the country for 5 days after sending the application

because application can be send via 2nd class post and not exactly right after you leave NCS office and you have to be physically present in the UK at the time UKBA gets it
it is NCS requirement to cover them in case you fly away, your passport will be scanned at the airport and UKBA will know, if they check it, you are not present in UK at the day they receive your application

That makes sense, thanks
I am attending NCS on 6th April and will be flying out of UK on 14th which should be ok.
NCS said that they will send it by special delivery next day and give me a tracking number.
Best regards