Can you please help me to make a reply to this letter saying that ...?

Question

.....the minister could not attend the meeting, and he would be represented by the ambassador of the country where the meeting is held. Thanks.
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Reference to my earlier letter dated 3rd December 2006 to Your Excellency inviting you to participate in the Roundtable on Energy in London on 5th June 2007.

I would like to take this opportunity to invite Your Excellency to make a 20 minutes intervention in the meeting.

In order to facilitate our discussion in the Roundtable, we have arranged a renowned consultant in the field of energy to prepare a background paper and present it to the Ministers.

I look forward to your positive response and to your participation in the Roundtable as well as the names of the members of your delegation .....................

Answer 1

My suggested and humble reply is as follows:

My dearest friend,

Thank you for inviting His Excellency to the Roundtable of Energy in London. I extend my sincere thanks to you.

However, It is with utmost regret to inform you that His Excellency cannot attend the meeting due to an important schedule that will be held on that particular date mentioned.

Nevertheless, His Excellency will be represented by the ambassador to participate in the discussion of the Roundtable on Energy.

In view of this matter, the ambassador is preparing to participate in the Roundtable on behalf of His Excellency.

I look forward to your correspondences.

Cordially,

Ron

Answer 2

Dear Sir,

Thank you for your kind invitation to participate in the Roundtable on Energy on 5th June 2007.

Unfortunately I am unable to attend, however, I will be represented by Mr .............., the Ambassador in London.

Yours faithfully,

Answer 3

I'd change Reference to Referencing. I'd also elaborate on the intervention requested of the person. Explain what is meant, how much time is allotted or what subjects may be discussed.

Answer 4

sound good to me just fill in the names