Closing down a company - what do I do?

[Aman]

What period does the CT return cover?

If it's a dormant period, just call HMRC and say "It was dormant" - job done

Thanks.
The return HMRC sent a [CT600?] return reminder for covers the period 1 July 2010 to 30 June 2011. My company bank account was closed on 20 Jan 2010, so I couldn't trade even if I wanted to. The accountant advised the HMRC and Companies House on submission of the 1 July2009 - 30 June 2010 accounts of the intention to close the company.
I telephoned Companies House and HMRC CT office and advised the company is dormant. Coudn't get either of them to acknowledge that returns aren't now required.

What exactly does 'dormant' mean, legally speaking?
Edit found it here,
http://www.hmrc.gov.uk/ct/getting-started/trading.htm
http://www.companieshouse.gov.uk/about/pdf/gba10.pdf

...so it looks like my company meets the criteria for dormancy.
Just as well, I can't make head nor tail of the CT600 form.